];-IANijBOOK  of 


For  Reference 


NOT  TO  BE  TAKEN  FROM  THIS  ROOM 


.^■■} 


Property  of 

N.  C.  COLLEGE  OF  AGRICULTURE 

Department- of  Zoology  and  Entonio!ogy 
No., 


Some  early  medical  entomology.     Athanasius  Kircher's  illustration  of  the  Italian  tarantula 
and  the  music  prescribed  as  an  antidote  for  the  poison  of  its  bite.     (1643). 


HANDBOOK  OF  MEDICAL 
ENTOMOLOGY 


WM.  A.  RILEY,  Ph.D. 

Professor  of  Insect  Morphology  and  Parasitology,  Cornell  University 
and 

O.  A.  JOHANNSEN,  Ph.D. 

Professor  of  Biology,  Cornell  University 


ITHACA,  NEW  YORK 

THE  COIVISTOCK  PUBLISHING  COMPANY 

1915 


COPYRIGHT,    I9I5 

BY  THE  COMSTOCK   PUBLISHING  COMPANY, 

ITHACA,    N.  Y. 


Press  of  W.  F.  Humphrey 
Geneva,  N.  Y. 


PREFACE 

THE  Handbook  of  Medical  Entomology  is  the  outgrowth  of  a 
course  of  lectiu^es  along  the  lines  of  insect  transmission  and 
dissemination  of  diseases  of  man  given  by  the  senior  author 
in  the  Department  of  EntomologA^  of  Cornell  University  diuing  the 
past  six  years.  More  specifically  it  is  an  illustrated  revision  and 
elaboration  of  his  "Notes  on  the  Relation  of  Insects  to  Disease" 
published  January,  191 2. 

Its  object  is  to  afford  a  general  survey  of  the  field,  and  primarily 
to  put  the  student  of  medicine  and  entomology  in  touch  with  the 
discoveries  and  theories  which  underlie  some  of  the  most  important 
modem  work  in  preventive  medicine.  At  the  same  time  the  older 
phases  of  the  subject — ^the  consideration  of  poisonous  and  parasitic 
forms — have  not  been  ignored. 

Considering  the  rapid  shifts  in  viewpoint,  and  the  development 
of  the  subject  within  recent  years,  the  authors  do  not  indulge  in  any 
hopes  that  the  present  text  will  exactly  meet  the  needs  of  every 
one  specializing  in  the  field,- — still  less  do  they  regard  it  as  complete 
or  final.  The  fact  that  the  enormous  literature  of  isolated  articles  is 
to  be  foimd  principally  in  foreign  periodicals  and  is  therefore  difficult 
of  access  to  many  American  w^orkers,  has  led  the  authors  to  hope 
that  a  summary  of  the  important  advances,  in  the  form  of  a  reference 
book  may  not  prove  unwelcome  to  physicians,  sanitarians  and 
working  entomologists,  and  to  teachers  as  a  text  supplementing 
lectiire  work  in  the  subject. 

Lengthy  as  is  the  bibliography,  it  covers  but  a  ver}'  small  fraction 
of  the  important  contributions  to  the  subject.  It  will  serve  onh'  to 
put  those  interested  in  touch  with  original  sources  and  to  open  up 
the  field.  Of  the  more  general  works,  special  acknowledgment 
should  be  made  to  those  of  Banks,  Bnimpt,  Castellani  and  Chalmers, 
Comstock,  Hewitt,  Howard,  Manson,  Mense,  Neveau-Lemaire, 
Nuttall,  and  Stiles. 

To  the  many  who  have  aided  the  authors  in  the  years  past,  by 
suggestions  and  by  sending  specimens  and  other  materials,  sincerest 
thanks  is  tendered.  This  is  especially  due  to  their  colleagues  in 
the  Department  of  Entomology  of  Cornell  University,  and  to  Pro- 
fessor Charles  W.  Howard,  Dr.  John  Uri  Lloyd,  Mr.  A.  H.  Ritchie, 
Dr.  I.  M.  Unger,  and  Dr.  Luzerne  Coville. 


VI  Preface 

They  wish  to  express  indebtedness  to  the  authors  and  publishers 
who  have  so  willingly  given  permission  to  use  certain  illustrations. 
Especially  is  this  acknowledgment  due  to  Professor  John  Henry 
Comstock,  Dr.  L.  O.  Howard,  Dr.  Graham-Smith,  and  Professor 
G.  H.  T.  Nuttall.  Professor  Comstock  not  only  authorized  the  use 
of  departmental  negatives  by  the  late  Professor  M.  V.  Slingerland 
(credited  as  M.  V.  S.),  but  generously  put  at  their  disposal  the  illus- 
trations from  the  Manual  for  the  Study  of  Insects  and  from 
the  Spider  Book.  Figures  5  and  iii  are  from  Peter's  "Der  Arzt 
und  die  Heilkunft  in  der  deutschen  Vergangenheit."  It  should  be 
noted  that  on  examining  the  original,  it  is  found  that  Gottfried's 
figure  relates  to  an  event  antedating  the  typical  epidemic  of  dancing 
mania. 

Wm.  a.  Riley. 
Cornell  University,  Q.  A.  Johannsen. 

January,  191 5. 


CONTENTS 
CHAPTER  I 
Early  suggestions  regarding  the  transmission  of  disease  by  insects. 


INTRODUCTION j_^ 


ADDITIONS  AND   CORRECTIONS 

vi  line  1 1,  for  Heilkunft  read  Heilkunst.  6-56 

18  line  2,  for  tarsi  read  tarsus. 

;i2  line  21,   and  legend   under   fig.   23,   for   C.    (Conorhinus) 

abdominalis  read  Melanolestes  abdominalis.  itrodectus.     Other 

47  legend  under  figure  for  33c  read  34. 

92  line  22  and  25,  for  sangiusugus  read  sanguisugus. 

116  legend  under  fig.  83,  for  Graham-Smith  read  Manson. 

136  line  10,  from  bottom,  insert  "ring"  after  "chitin". 

137  line  3,  for  meditatunda  read  meditabunda. 
145  line  7,  from  bottom,  for  Rs  read  R,.. 

158  line  20,  for  have  read  has. 

212  after  the  chapter  heading  insert  "continued". 

219  line  10,  from  bottom,  for  Cornohinus  read  Conorhinus. 

266  line  I,  fig.  158J  refers  to  the  female. 

272  line  5,  insert  "palpus"  before  "and  leg". 

281  line  6,  for  discodial  read  discoidal.  .  or  giant   water- 

281  last  line,  insert  "from"  before  "the".  •   .  .    , 

284  line  5,  for  "tubercle  of"  read  "tubercle  or".  miptera    reported 

305  lines  19,  28,  44,  page  306  lines  i,  9,  22,  27,  30,  page  307  line  7, 

page  309  lines  8,  1 1,  for  R4+5  read  M^+^. 

309  legend  under  fig.  168  add  Bureau  of  Entomology. 

312  line  36,  for  "near  apex"  read  "of  M,-i-j.". 

313  rvmning  head,  for  Muscidse  read  Muscoidea. 

314  line  29,  for  "distal  section"  read  "distally  M^+^". 

315  legend  under  fig.   172,  for  Pseudopyrellia  read  Orthellia,  soning  by  nettling 

for  Lvperosia  read  Hasmatobia,  for  Umbana  read  urbana. 
323  and^325^^  legends  under  the  figures,  add  "After  Dr.  J.  H.  ^^-^  ^lood  plasma. 

328     line  7  from  bottom  for  Apiochaeta  read  Aphiochseta. 


PARASITIC  ARTHROPODS  AFFECTING  MAN 57-130 

Acarina,  or  mites. 

The  TrombidiidcB,  or  harvest  mites. 
The  Ixodoidea,  or  ticks. 

Argasidas.     Ixodidje.     Treatment  of  tick  bites. 
The  mites. 

Dermanyssidae.     Tarsonemid^e.     Sarcoptidse,   the  itch  mites.     Demode- 
cidae,  the  follicle  mites. 
Hexapoda,  or  true  insects. 
vSiphunculata,  or  sucking  lice. 
Hemiptera. 


VI  Preface 

They  wish  to  express  indebtedness  to  the  authors  and  publishers 
who  have  so  wilHngh^  given  permission  to  use  certain  illustrations. 
Especially  is  this  acknowledgment  due  to  Professor  John  Henry 
Comstock,  Dr.  L.  0.  Howard,  Dr.  Graham-Smith,  and  Professor 
G.  H.  T.  Nuttall.  Professor  Comstock  not  only  authorized  the  use 
of  departmental  negatives  by  the  late  Professor  M.  V.  Slingerland 

(credited  as  M.  V.  S.),  b  " "■""  ^""-^  "^  ^-^"--^  Hkt^ncinl  the  ilhis- 

trations  from  the  Mant 
the  Spider  Book.  Fig^ 
und  die  Heilkunft  in  de 
noted  that  on  examinin 
figure  relates  to  an  exen 
mania. 

Cornell  University, 
Januaty,  191 5. 


CONTENTS 

CHAPTER  I 

INTRODUCTION 1-5 

Early  suggestions  regarding  the  transmission  of  disease  by  insects. 
The  ways  in  which  arthropods  may  affect  the  health  of  man. 

CHAPTER  II 
ARTHROPODS  WHICH  ARE  DIRECTLY  POISONOUS 6-56 

The  Araneida,  or  Spiders. 

The  tarantulas.     Bird  spiders.     Spiders  of  the  genus  Latrodectus.     Other 
venomous  spiders.     Summary. 
The  Pedipalpida,  or  whip-scorpions. 
The  Scorpionida,  or  true  scorpions. 
The  Solpugida,  or  solpugids. 
The  Acarina,  or  mites  and  ticks. 
The  Myriapoda,  or  centipedes  and  millipedes. 
The  Hexapoda,  or  true  insects. 

Piercing  or  biting  insects  poisonous  to  man. 
Hemiptera,  or  true  bugs. 

The  Notonectidae  or  back-swimmers.     Belostomidae  or  giant   water- 
bugs.     Reduviidae,    or    assassin    bugs.     Other  Hemiptera    reported 
as  poisonous  to  man. 
Diptera;   the  midges,  mosquitoes  and  flies. 
Stinging  insects. 

Apis  melliiica,  the  honey  bee.     Other  stinging  forms. 
Nettling  insects. 

Lepidoptera,  or  butterflies  and  moths.     Relief  from  poisoning  by  nettling 
larvs. 
Vescicating  insects  and  those  possessing  other  poisons  in  their  blood  plasma. 
The  blister  beetles.     Other  cryptotoxic  insects. 

CHAPTER  III 
PARASITIC  ARTHROPODS  AFFECTING  MAN 57-130 

Acarina,  or  mites. 

The  Trombidiidse,  or  harv^est  mites. 
The  Ixodoidea,  or  ticks. 

Argasidae.     Ixodidae.     Treatment  of  tick  bites. 
The  mites. 

Dermanyssidae.     Tarsonemidse.     Sarcoptidae,   the  itch   mites.     Demode- 
cidae,  the  follicle  mites. 
Hexapoda,  or  true  insects. 
.Siphunculata,  or  sucking  lice. 
Hemiptera. 


VIII  Contents 

The  bed-bug.     Other  bed-bugs. 
Parasitic  Diptera,  or  flies. 

Psychodidse,   or  moth  flies.     Phlebotominae.      Culicidfc,   or  mosquitoes. 
Simuliidse,    or    black-flies.     Chironomidag,    or    midges.     TabanidiE,    or 
horse-flies.     Leptidas  or  snipe-flies.     Oestridas,  or  bot-flies.     Muscidae, 
the  stable-fly  and  others. 
Siphonaptera,  or  fleas. 

The  fleas  affecting  man,  the  dog,  cat,  and  rat. 
The  true  chiggers,  or  chigoes. 

CHAPTER  IV 
ACCIDENTAL  OR  FACULTATIVE  PARASITES 1^1-143 

Acarina,  or  mites. 

Myriapoda,  or  centipedes  and  millipedes. 

Lepidopterous  larvae. 

Coleoptera,  or  beetles. 

Dipterous  larvae  causing  myiasis. 

Piophila  casei,  the  cheese  skipper.  Chr>^somyia  macellaria,  the  screw- 
worm  fly.  Calliphorinas,  the  blue-bottles.  Muscinag,  the  house  or 
typhoid  fly,  and  others.  Anthomyiidae,  the  lesser  house-fly  and  others. 
Sarcophagidag,  the  flesh-flies. 

CHAPTER  V 

ARTHROPODS  AS  SIMPLE  CARRIERS  OF  DISEASE 144-163 

The  house  or  typhoid  fly  as  a  carrier  of  disease. 

Stomoxys  calcitrans,  the  stable-fly. 

Other  arthropods  which  may  serve  as  simple  carriers  of  pathogenic  organisms. 

CHAPTER  VI 
ARTHROPODS  AS  DIRECT  INOCULATORS  OF  DISEASE  GERMS  164-174 
Some  illustrations  of  direct  inoculations  of  disease  germs  by  arthropods. 
The  r&le  of  fleas  in  the  transmission  of  the  plague. 

CHAPTER  VII 
ARTHROPODS  AS  ESSENTIAL  HOSTS  OF  PATHOGENIC  ORGAN- 
ISMS      175-185 

Insects  as  intermediate  hosts  of  tape-worms. 

Arthropods  as  intermediate  hosts  of  nematode  worms.     Filariasis  and  mosqui- 
toes. 
Other  nematode  parasites  of  man  and  animals. 

CHAPTER  VIII 

ARTHROPODS   AS   ESSENTIAL    HOSTS    OF  PATHOGENIC   PRO- 
TOZOA      186-21 1 

Mosquitoes  and  malaria. 
Mosquitoes  and  yellow  fever. 


Contents  IX 

CHAPTER  IX 
ARTHROPODS   AS   ESSENTIAL   HOSTS    OF   PATHOGENIC   PRO- 
TOZOA         212-22y 

Insects  and  ttypanosomiases. 

Fleas  and  lice  as  carriers  of  Trypanosoma  lewisi. 

Tsetse-flies  and  nagana. 

Tsetse-flies  and  sleeping  sickness  in  man. 

South  American  trypanosomiasis. 

Leishmanioses  and  insects. 
Ticks  and  diseases  of  man  and  animals. 

Cattle  tick  and  Texas  fever. 

Ticks  and  Rocky  Mountain  Spotted  fever  of  man. 

CHAPTER  X 
ARTHROPODS  AS  ESSENTIAL  HOSTS  OF  PATHOGENIC  PROTO- 
ZOA (Continued) 230-240 

Arthropods  and  Spirochsetoses  of  man  and  animals. 

African  relapsing  fever  of  man. 

European  relapsing  fever. 

North  African  relapsing  fever  of  man. 

Other  types  of  relapsing  fever  of  man. 

Spirochetosis  of  fowls. 

Other  spirochsete  diseases  of  animals. 
Typhus  fever  and  lice. 

CHAPTER  XI 
SOME     POSSIBLE,     BUT     IMPERFECTLY     KNOWN     CASES     OF 

ARTHROPOD    TRANSMISSION    OF    DISEASE 241-256 

Infantile  paralysis,  or  acute  anterior  poliomyelitis. 
Pellagra.     Leprosy.     Verruga  peruviana.     Cancer. 

CHAPTER  XII 

KEYS  TO  THE  ARTHROPODS  NOXIOUS  TO  MAN 257-317 

Crustacea. 

Myriapoda,  or  centipedes  and  millipedes. 

Arachnida  (Orders  of) . 

Acarina  or  ticks. 
Hexapoda  (Insecta). 

Siphunculata  and  Hemiptera  (lice  and  true  bugs). 
Diptera  (mosquitoes,  midges,  and  flies). 
Siphonaptera  (fleas). 

APPENDIX 

Hydrocyanic  acid  gas  against  household  insects 318-320 

Proportion  of  ingredients.     A  single  room  as    an    example.     Fumigating  a 
large  house.     Precautions. 
Lesions  produced  by  the  bite  of  the  black-fly 321-326 

BIBLIOGRAPHY    327-340 

INDEX 341-348 


CHAPTER  I. 
INTRODUCTION 

EARLY  SUGGESTIONS  REGARDING  THE  TRANSMISSION  OF  DISEASE 

BY  INSECTS 

Until  very  recent  3^ears  insects  and  their  allies  have  been  considered 
as  of  economic  importance  merely  in  so  far  as  they  are  an  annoyance 
or  direct  menace  to  man,  or  his  flocks  and  herds,  or  are  injurious  to 
his  crops.  It  is  only  within  the  past  fifteen  years  that  there  has 
sprung  into  prominence  the  knowledge  that  in  another  and  much  more 
insiduous  manner,  they  may  be  the  enemy  of  mankind,  that  they 
may  be  among  the  most  important  of  the  disseminators  of  disease. 
In  this  brief  period,  such  knowledge  has  completely  revolutionized 
our  methods  of  control  of  certain  diseases,  and  has  become  an  import- 
ant weapon  in  the  fight  for  the  conservation  of  health. 

It  is  nowhere  truer  than  in  the  case  under  consideration  that  how- 
ever abrupt  may  be  their  coming  into  prominence,  great  move- 
ments and  great  discoveries  do  not  arise  suddenly.  Centuries  ago 
there  was  suggested  the  possibility  that  insects  were  concerned  with 
the  spread  of  disease,  and  from  time  to  time  there  have  appeared  keen 
suggestions  and  logical  hypotheses  along  this  line,  that  lead  us  to 
marvel  that  the  establishment  of  the  truths  should  have  been  so  long 
delayed. 

One  of  the  earliest  of  these  references  is  by  the  Italian  physician,. 
Mercurialis,  who  lived  from  1530  to  1607,  during  a  period  when 
Europe  was  being  ravaged  by  the  dread  "black  death",  or  plague. 
Concerning  its  transmission  he  wrote:  "There  can  be  no  doubt  that 
flies  feed  on  the  internal  secretions  of  the  diseased  and  dying,  then, 
flying  away,  they  deposit  their  excretions  on  the  food  in  neighboring 
dwellings,  and  persons  who  eat  of  it  are  thus  infected." 

It  would  be  difficult  to  formulate  more  clearly  this  aspect  of  the 
facts  as  we  know  them  to-day,  though  it  must  always  be  borne  in 
mind  that  we  are  prone  to  interpret  such  statements  in  the  light  of 
present-day  knowledge.  Mercurialis  had  no  conception  of  the  animate 
nature  of  contagion,  and  his  statement  was  little  more  than  a  lucky 
guess. 

Much  more  worthy  of  consideration  is  the  approval  which  was 
given  to  his  view  by  the  German  Jesuit,  Athanasius  Kircher  in  1658. 


2  Introduction 

One  cannot  read  carefiilly  his  works  without  beHeving  that  long 
before  Leeuwenhook's  discovery,  Kircher  had  seen  the  larger  species  of 
bacteria.  Moreover,  he  attributed  the  production  of  disease  to  these 
organisms  and  formulated,  vaguely,  to  be  sure,  a  theorv^  of  the  animate 
nature  of  contagion.  It  has  taken  two  and  a  half  centuries  to 
accumulate  the  facts  to  prove  his  hypothesis. 

The  theory  of  Mercuriahs  was  not  wholly  lost  sight  of,  for  in  the 
medical  literattire  of  the  eighteenth  century  there  are  scattered 
references  to  flies  as  carriers  of  disease.  Such  a  view  seems  even  to 
have  been  more  or  less  popularly  accepted,  in  some  cases.  Gudger 
(1910),  has  pointed  out  that,  as  far  back  as  1769,  Edward  Bancroft, 
in  "An  Essay  on  the  Natural  History  of  Guiana  in  South  America," 
wrote  concerning  the  contagious  skin-disease  known  as  "Yaws": 
"It  is  usually  believed  that  this  disorder  is  communicated  by  the  flies 
who  have  been  feasting  on  a  diseased  object,  to  those  persons  who  have 
sores,  or  scratches,  which  are  uncovered;  and  from  many  observ^a- 
tions,  I  think  this  is  not  improbable,  as  none  ever  receive  this  disorder 
whose  skins  are  whole." 

Approaching  more  closely  the  present  epoch,  we  find  that  in  1848, 
Dr.  Josiah  Nott,  of  Mobile,  Alabama,  published  a  remarkable 
article  on  the  cause  of  yellow  fever,  in  which  he  presented  "reasons  for 
supposing  its  specific  cause  to  exist  in  some  form  of  insect  life." 
As  a  matter  of  fact,  the  bearing  of  Nott's  work  on  present  day  ideas 
of  the  insect  transmission  of  disease  has  been  very  curiously  overrated. 
The  common  interpretation  of  his  theory  has  been  deduced  from  a  few 
isolated  sentences,  but  his  argtunent  appears  quite  differently  when 
the  entire  article  is  studied.  It  must  be  remembered  that  he  wrote  at 
a  period  before  the  epoch-making  discoveries  of  Pasteur  and  before 
the  recognition  of  micro-organisms  as  factors  in  the  cause  of  disease. 
His  article  is  a  masterly  refutation  of  the  theory  of  "malarial"  origin 
of  "all  the  fevers  of  hot  climates,"  but  he  uses  the  term  "insect"  as 
applicable  to  the  lower  forms  of  life,  and  specific  references  to  "mos- 
quitoes," "aphids,""  cotton-worms,"  and  others,  are  merely  in  the 
way  of  similes. 

But,  while  Nott's  ideas  regarding  the  relation  of  insects  to  yellow 
fever  were  vague  and  indefinite,  it  was  almost  contemporaneously 
that  the  French  physician,  Louis  Daniel  Beauperthuy  argued  in  the 
most  explicit  possible  manner,  that  yellow  fever  and  various  others 
are  transmitted  by  mosquitoes.  In  the  light  of  the  data  which  were 
available  when  he  wrote,  in  1853,  it  is  not  stuprising  that  he  erred  by 


Early  Suggestions  3 

thinking  that  the  source  of  the  virus  was  decomposing  matter  which 
the  mosquito  took  up  and  accidentally  inoculated  into  man.  Beau- 
perthuy  not  only  discussed  the  role  of  mosquitoes  in  the  transmission 
of  disease,  but  he  taught,  less  clearly,  that  house-flies  scatter  patho- 
genic organisms.  It  seems  that  Boyce  (1909)  who  quotes  extensively 
from  this  pioneer  work,  does  not  go  too  far  when  he  says  "It  is  Dr. 
Beauperthuy  whom  we  must  regard  as  the  father  of  the  doctrine  of 
insect-borne  disease." 

In  this  connection,  mention  must  be  made  of  the  scholarly  article 
by  the  American  physician,  A.  F.  A.  King  who,  in  1883,  brought 
together  an  all  but  conclusive  mass  of  argument  in  support  of  his 
belief  that  malaria  was  caused  by  mosquitoes.  At  about  the  same 
time,  Finley,  of  Havana,  was  forcefully  presenting  his  view  that  the 
mosquito  played  the  chief  role  in  the  spread  of  yellow  fever. 

To  enter  more  fully  into  the  general  historical  discussion  is  beyond 
the  scope  of  this  book.  We  shall  have  occasion  to  make  more 
explicit  references  in  considering  various  insect-borne  diseases. 
Enough  has  been  said  here  to  emphasize  that  the  recognition  of 
insects  as  factors  in  the  spread  of  disease  was  long  presaged,  and  that 
there  were  not  wanting  keen  thinkers  who,  with  a  background  of 
present-day  conceptions  of  the  nature  of  disease,  might  have  been  in 
the  front  rank  of  investigators  along  these  lines. 

THE   WAYS   IN   WHICH   ARTHROPODS    MAY  AFFECT    THE    HEALTH 

OF  MAN 

When  we  consider  the  ways  in  which  insects  and  their  allies  may 
affect  the  health  of  man,  we  find  that  we  may  treat  them  under  three 
main  groups: 

A.  They  may  be  directly  poisonous.  Such,  for  example,  are  the 
scorpions,  certain  spiders  and  mites,  some  of  the  predaceous  bugs, 
and  stinging  insects.  Even  such  forms  as  the  mosquito  deserve 
some  consideration  from  this  viewpoint. 

B.  They  may  be  parasitic,  living  more  or  less  permanently  on 
or  in  the  body  and  deriving  their  sustenance  from  it. 

Of  the  parasitic  arthropods  we  may  distinguish,  first,  the  trtie 
parasites,  those  which  have  adopted  and  become  confirmed  in  the 
parasitic  habit.  Such  are  the  itch  mites,  the  lice,  fleas,  and  the 
majority  of  the  forms  to  be  considered  as  parasitic. 

In  addition  to  these,  we  may  distinguish  a  group  of  accidental,  or 
facultative  parasites,  species  which  are  normally  free-living,  feeding  on 


4  Introduction 

decaying  substances,  but  which  when  accidentally  introduced  into 
the  alimentary  canal  or  other  cavities  of  man,  may  exist  there 
for  a  greater  or  less  period.  For  example,  certain  fly  larvae,  or  mag- 
gots, normally  feeding  in  putrifying  meat,  have  been  known  to  occur 
as  accidental  or  facultative  parasites  in  the  stomach  of  man. 

C.  Finally,  and  most  important,  arthropods  may  be  trans- 
mitters and  disseminators  of  disease.  In  this  capacity  the^^  may 
function  in  one  of  three  ways;  as  simple  carriers,  as  direct  inoculators, 
or  as  essential  hosts  of  disease  germs. 

As  simple  carriers,  they  may,  in  a  wholly  incidental  manner, 
transport  from  the  diseased  to  the  healthy,  or  from  filth  to  food, 
pathogenic  germs  which  cling  to  their  bodies  or  appendages.  Such, 
for  instance,  is  the  relation  of  the  house-fly  to  the  dissemination  of 
typhoid. 

As  direct  inoculators,  biting  or  piercing  species  may  take  up  from 
a  diseased  man  or  animal,  germs  which,  clinging  to  the  mouth  parts, 
are  inoculated  directly  into  the  blood  of  the  insect's  next  victim.  It 
it  thus  that  horse-flies  may  occasionally  transmit  anthrax.  Similarly, 
species  of  spiders  and  other  forms  which  are  ordinarily  perfectly 
harmless,  may  accidentally  convey  and  inoculate  pyogenic  bacteria. 

It  is  as  essential  hosts  of  disease  germs  that  arthropods  play  their 
most  important  role.  In  such  cases  an  essential  part  of  the  life  cycle 
of  the  pathogenic  organism  is  undergone  in  the  insect.  In  other 
words,  without  the  arthropod  host  the  disease-producing  organism 
cannot  complete  its  development.  As  illustrations  may  be  cited  the 
relation  of  the  Anopheles  mosquito  to  the  malarial  parasite,  and  the 
relation  of  the  cattle  tick  to  Texas  fever. 

A  little  consideration  will  show  that  this  is  the  most  important  of 
the  group.  Typhoid  fever  is  carried  by  water  or  by  contaminated 
milk,  and  in  various  other  ways,  as  well  as  by  the  house-fly.  Kill  all 
the  house-flies  and  typhoid  woiild  still  exist.  On  the  other  hand, 
malaria  is  carried  only  by  the  mosquito,  because  an  essential  part  of 
the  development  of  the  malarial  parasite  is  undergone  in  this  insect. 
Exterminate  all  of  the  mosquitoes  of  certain  species  and  the  dis- 
semination of  human  malaria  is  absolutely  prevented. 

Once  an  arthropod  becomes  an  essential  "host  for  a  given  parasite 
it  may  disseminate  infection  in  three  different  ways : 

I.  By  infecting  man  or  animals  who  ingest  it.  It  is  thus,  for 
example,  that  man,  dog,  or  cat,  becomes  infected  with  the  double- 
pored  dog  tapeworm,  Dipylidium  caninum.     The  cysticercoid  stage 


Arthropods  and  Man  5 

occurs  in  the  dog  louse,  or  in  the  dog  or  cat  fleas,  and  by  accidentally 
ingesting  the  infested  insect  the  vertebrate  becomes  infested.  Simi- 
larly, Hymenolepis  diminuta,  a  common  tapeworm  of  rats  and  mice, 
and  occasional  in  man,  undergoes  part  of  its  hfe  cycle  in  various  meal- 
infesting  insects,  and  is  accidentally  taken  up  by  its  definitive  host. 
It  is  very  probable  that  man  becomes  infested  with  Dracunculus 
(Filaria)  tnedinensis  through  swallowing  in  drinking  water,  the 
crustacean,  Cyclops,  containing  the  larvae  of  this  worm. 

2.  By  infecting  man  or  animals  on  whose  skin  or  mucous  mem- 
branes the  insect  host  may  be  crushed  or  may  deposit  its  excrement. 
The  pathogenic  organism  may  then  actively  penetrate,  or  may  be 
inoculated  by  scratching.  The  causative  organism  of  typhus  fever 
is  thus  transmitted  by  the  body  louse. 

3.  By  direct  inoculation  by  its  bite,  the  insect  host  may  transfer 
the  parasite  which  has  undergone  development  within  it.  The 
malarial  parasite  is  thus  transferred  by  mosquitoes;  the  Texas  fever 
parasite  by  cattle  ticks. 


CHAPTER  II. 

ARTHROPODS   WHICH  ARE   DIRECTLY  POISONOUS 

Of  all  the  myriads  of  insects  and  related  forms,  a  ^^ery  few  are  of 
direct  use  to  man,  some  few  others  have  forced  his  approbation  on 
accotmt  of  their  wonderftd  beauty,  but  the  great  hordes  of  them  are 
loathed  or  regarded  as  directly  dangerous.  As  amatter  of  fact,  only 
a  very,  small  ntmiber  are  in  the  slightest  degree  poisonous  to  man  or 
to  the  higher  animals.  The  result  is  that  entomologists  and  lovers 
of  nature,  intent  upon  dissipating  the  foolish  dread  of  insects,  are 
sometimes  inclined  to  go  to  the  extreme  of  discrediting  all  statements 
of  serious  injury  from  the  bites  or  stings  of  any  species. 

Nevertheless,  it  must  not  be  overlooked  that  poisonous  forms  do 
exist,  and  they  must  recei^^e  attention  in  a  consideration  of  the  wa3^s 
in  which  arthropods  may  affect  the  health  of  man.  Moreover,  it 
must  be  recognized  that  "what  is  one  man's  meat,  is  another  man's 
poison,"  and  that  in  considering  the  possibilities  of  injury  we  must  not 
ignore  individual  idiosyncrasies.  Just  as  certain  individuals  may  be 
poisoned  by  what,  for  others  are  common  articles  of  food,  so  some 
persons  may  be  abnormally  susceptible  to  insect  poison.  Thus,  the 
poison  of  a  bee  sting  may  be  of  varying  severity,  but  there  are  individ- 
uals who  are  made  seriously  sick  by  a  single  sting,  regardless  of  the 
point  of  entr>' .  Some  individuals  scarcely  notice  a  mosquito  bite, 
others  find  it  ven*'  painful,  and  so  illustrations  of  this  difference  in 
individuals  might  be  multiplied. 

In  considering  the  poisonous  arthropods,  we  shall  take  them  up  by 
groups.  The  reader  who  is  unacquainted  with  the  systematic  rela- 
tionship of  insects  and  their  allies  is  referred  to  Chapter  XII.  No 
attempt  will  be  made  to  make  the  lists  under  the  various  headings 
exhaustive,  but  typical  forms  wnll  be  discussed. 

ARANEIDA   OR   SPIDERS 

Of  aU  the  arthropods  there  are  none  which  are  more  tmiversalh" 
feared  than  are  the  spiders.  It  is  commonly  supposed  that  the 
majority,  if  not  all  the  species  are  poisonous  and  that  they  are  aggres- 
sive enemies  of  man  and  the  higher  animals,  as  weU  as  of  lower  forms. 

That  they  really  secrete  a  poison  ma>'  be  readily  inferred  from  the 
effect  of  their  bite  upon  insects  and  other  small  forms.     Moreover, 


Araneida  or  Spiders 


Head  of  a  spider  showing 
poison  gland  (c)  and  its  re- 
lation to  the  chelicera  (a). 


the  presence  of  definite  and  well-developed  poison  glands  can  easily 
be  shown.  They  occur  as  a  pair  of  pouches  (fig.  i)  lying  within  the 
cephalothorax  and  connected  by  a  delicate 
duct  with  a  pore  on  the  claw  of  the  chelicera, 
or  so-called  "  mandible"  on  the  convex  surface 
of  the  claw  in  such  a  position  that  it  is  not 
plugged  and  closed  by  the  flesh  of  the  victim. 
The  glands  may  be  demonstrated  by  slowly 
and  carefully  twisting  off  a  chelicera  and 
pushing  aside  the  stumps  of  muscles  at  its 
base.  By  exercising  care,  the  chitinous  wall 
of  the  chelicera  and  its  claw  may  be  broken 
away  and  the  duct  traced  from  the  gland  to  its  outlet.  The  inner 
lining  of  the  sac  is  constituted  by  a  highly  developed  glandular 
epithelitmi,  supported  by  a  basement  membrane  of  connective 
tissue  and  covered  by  a  musctdar  layer,  (fig.  2).  The  muscles,  which 
are  striated,  are  spirally  arranged  (fig.  i),  and  are  doubtless  under 
control  of  the  spider,  so  that  the  amount  of  poison  to  be  injected  into 
a  wound  may  be  varied. 

The  poison  itself,  according  to  Robert  (1901),  is  a  clear,  colorless 
fluid,  of  oily  consistency,  acid  reaction,  and  ver\^  bitter  taste.  After 
the  spider  has  bitten  two  or  three  times,  its  supply  is  exhausted  and 
therefore,  as  in  the  case  of  snakes,  the  poison  of  the  bite  decreases 
quickly  with  use,  until  it  is  null.  To  what  extent  the  content  of  the 
poison  sacs  may  contain  blood  serum  or,  at  least,  active  principles  of 
serum,  in  addition  to  a  specific  poison  formed  by  the  poison  glands 
themselves,  Kobert  regards  as  an  open'  question.  He  believes  that 
the  acid  part  of  the  poison,  if  reall}^  present, 
is  formed  by  the  glands  and  that, 
in  the  case  of  some  spiders,  the 
ferment -like,  or  better,  active 
toxine,  comes  from  the  blood. 

But  there  is  a  wide  difference 
between  a  poison  which  ma}'  kill 
an  insect  and  one  which  is  harm- 
ful to  men.  Certain  it  is  that 
there  is  no  lack  of  popular  belief 
and  newspaper  records  of  fatal 
cases,  but  the  evidence  regarding  the  possibility  of  fatal  or  even  very 
serious  results  for  man  is  most  contradictory.  For  some  years, 
we    have    attempted  to  trace  the  more  circumstantial  newspaper 


3.  Chelicera   of 
spider. 


Section  through  a  venom 
gland  of  Latrodectus 
13-guttatus  showing 
the  peritoneal,  muscu- 
lar and  epithelial  layers. 
After  Bordas. 


8 


Poisonous  Arthropods 


accounts,  which  have  come  to  our  notice,  of  injury  by  North 
American  species.  The  results  have  served,  mainly,  to  empha- 
size the  straits  to  which  reporters  are  sometimes  driven  when 
there  is  a  dearth  of  news.  The  accounts  are  usually  vague  and  lack- 
ing in  any  definite  clue  for  locating  the  supposed  victim.  In  the 
comparatively  few  cases  where  the  patient,  or  his  physician,  could 
be  located,  there  was  either  no  claim  that  the  injury  was  due  to 
spider  venom,  or  there  was  no  evidence  to  support  the  belief. 
Rarely,  there  was  evidence  that  a  secondary  blood  poisoning,  such 
as  might  be  brought  about  by  the  prick  of  a  pin,  or  by  any  mechani- 
cal injury,  had  followed  the  bite  of  a  spider.     Such  instances  have 

no  bearing  on  the  question  of  the 
venomous  nature  of  these  forms. 
The  extreme  to  which  unreason- 
able fear  of  the  bites  of  spiders 
influenced  the  popular  mind  was 
evidenced  by  the  accepted  explana- 
tion of  the  remarkable  dancing 
mania,  or  tarantism,  of  Italy  during 
the  Middle  Ages.  This  was  a  ner- 
vous disorder,  supposed  to  be  due 
to  the  bite  of  a  spider,  the  European 
tarantula  (fig.  4),  though  it  was 
also,  at  times,  attributed  to  the 
bite  of  the  scorpion.  In  its  typical 
form,  it  was  characterized  by  so 
great  a  sensibility  to  music  that  under  its  influence  the  victims 
indulged  in  the  wildest  and  most  frenzied  dancing,  until  they  sank 
to  the  ground  utterly  exhausted  and  almost  lifeless.  The  profuse 
perspiring  resulting  from  these  exertions  was  supposed  to  be  the 
only  efficacious  remedy  for  the  disease.  Certain  forms  of  music 
were  regarded  as  of  especial  value  in  treating  this  tarantism,  and 
hence  the  name  of  "  tarantella"  was  applied  to  them.  Our  frontis- 
piece, taken  from  Athanasius  Kircher's  Magnes  sive  de  Arte  Magnetica, 
1643  ed.,  represents  the  most  commonly  implicated  spider  and  illus- 
trates some  of  what  Fabre  has  aptly  designated  as  "medical 
choreography." 

The  disease  was,  in  reality,  a  form  of  hysteria,  spreading  by  sym- 
pathy until  whole  communities  were  involved,  and  was  paralleled  by 
the  outbreaks  of  the  so-called  St.  Vitus's  or  St.  John's  dance,  which 


The  Italian  tarantula  (Lycosa  tarantula). 
After  Kobert. 


Araneida  or  Spiders  •  9 

swept  Germany  at  about  the  same  time  (fig.  5).  The  evidence  that 
the  spider  was  the  cause  of  the  first  is  about  as  conclusive  as  is  that 
of  the  demoniacal  origin  of  the  latter.  The  true  explanation  of  the 
outbreaks  is  doubtless  to  be  found  in  the  depleted  physical  and  mental 
condition  of  the  people,  resulting  from  the  wars  and  the  frightful 
plagues  which  devastated  all  Europe  previous  to,  and  during  these 
times.  An  interesting  discussion  of  these  aspects  of  the  question  is  to 
be  found  in  Hecker. 


5.     Dancing  mania.     Illustration  from  Johann  Ludwig  Gottfried's  Chronik.  1632. 

So  gross  has  been  the  exaggeration  and  so  baseless  the  poprdar  fear 
regarding  spiders  that  entomologists  have  been  inclined  to  discredit 
all  accounts  of  serious  injury  from  their  bites.  Not  only  have  the 
most  circumstantial  of  newspaper  accounts  proved  to  be  without 
foundation  but  there  are  on  record  a  number  of  cases  where  the  bite 
of  many  of  the  commoner  species  have  been  intentionally  provoked 
and  where  the  effect  has  been  insignificant.  Some  years  ago  the 
senior  author  personally  experimented  with  a  number  of  the  largest  of 
our  northern  species,  and  with  unexpected  results.  The  first  surprise 
was  that  the  spiders  were  very  unwilling  to  bite  and  that  it  required  a 
considerable  effort  to  get  them  to  attempt  to  do  so.     In  the  second 


lo  '  Poisonous  Arthropods 

place,  most  of  those  experimented  with  were  unable  to  pierce  the  skin 
of  the  palm  or  the  back  of  the  hand,  but  had  to  be  applied  to  the  thin 
skin  between  the  fingers  before  they  were  able  to  draw  blood.  Unfor- 
tunately, no  special  attempt  was  made  to  determine,  at  the  time,  the 
species  experimented  with,  but  among  them  were  Theridion  tepi- 
dariorum,  Miranda  aurantia  {Argiopa)  ,Metargiope  trifasciata,  Marxia 
stellata,  Aranea  irifoUum,  Misumena  vatia,  and  Agelena  ncBvia.  In 
no  case  was  the  bite  more  severe  than  a  pin  prick  and  though  in  some 
cases  the  sensation  seemed  to  last  longer,  it  was  probably  due  to  the 
fact  that  the  mind  was  intent  upon  the  experiment. 

Similar  experiments  were  carried  out  by  Blackwell  (1855),  who 
believed  that  in  the  case  of  insects  bitten,  death  did  not  result  any 


6.     An  American  tarantula  (Eurypelma  hentzii).     Natural  size.     After  Comstock 

more  promptly  than  it  would  have  from  a  purely  mechanical  injury  of 
equal  extent.  He  was  inclined  to  regard  all  accounts  of  serious 
injury  to  man  as  baseless.  The  question  cannot  be  so  summarily 
dismissed,  and  we  shall  now  consider  some  of  the  groups  which  have 
been  more  explicitly  implicated. 

The  Tarantulas. — In  popular  usage,  the  term  "  tarantula  "  is 
loosely  applied  to  any  one  of  a  ntmiber  of  large  spiders.  The  famous 
tarantulas  of  southern  Europe,  whose  bites  were  supposed  to  cause  the 
dancing  mania,  were  Lycosidce,  or  wolf-spiders.  Though  various 
species  of  this  group  were  doubtless  so  designated,  the  one  which 
seems  to  have  been  most  implicated  was  Lycosa  tarantula  (L.), 
(fig.  4).  On  the  other  hand,  in  this  country,  though  there  are  many 
Lycosidee,  the  term  "tarantula"  has  been  applied  to  members  of  the 
superfamily  Avicularoidea  (fig.  6),  including  the  bird-spiders. 

Of  the  Old  World  Lycosidae  there  is  no  doubt  that  several  species 
were  implicated  as  the  supposed  cause  of  the  tarantism.  In  fact,  as 
we  have  already  noted,  the  blame  was  sometimes  attached  to  a  scor- 


The  Tarantulas  ii 

pion.  However,  there  seems  to  be  no  doubt  that  most  of  the  accounts 
refer  to  the  spider  known  as  Lycosa  tarantula. 

There  is  no  need  to  enter  into  further  details  here  regarding  the 
supposed  xarulence  of  these  forms,  popular  and  the  older  medical 
literature  abound  in  circumstantial  accounts  of  the  terrible  effects  of 
the  bite.  Fortunately,  there  is  direct  experimental  evidence  which 
bears  on  the  question. 

Fabre  induced  a  common  south  European  wolf-spider,  Lycosa 
narhonensis ,  to  bite  the  leg  of  a  young  sparrow,  ready  to  leave  the 
nest.  The  leg  seemed  paralyzed  as  a  result  of  the  bite,  and  though 
the  bird  seemed  lively  and  clamored  for  food  the  next  day,  on  the 
third  day  it  died.  A  mole,  bitten  on  the  nose,  succumbed  after  thirty- 
six  hours.  From  these  experiments  Fabre  seemed  justified  in  his 
conclusion  that  the  bite  of  this  spider  Is  not  an  accident  which  man 
can  afiford  to  treat  lightly.  Unforttmately,  there  is  nothing  in  the 
experiments,  or  in  the  symptoms  detailed,  to  exclude  the  probability 
that  the  death  of  the  animals  was  the  result  of  secondary  infection. 

As  far  back  as  1693,  as  we  learn  from  the  valuable  account  of 
Robert,  (1901),  the  Italian  physician,  Sanguinetti  allowed  himself  to 
be  bitten  on  the  arm  by  two  tarantulas,  in  the  presence  of  witnesses. 
The  sensation  was  equivalent  to  that  from  an  ant  or  a  mosquito  bite 
and  there  were  no  other  phenomena  the  first  day.  On  the  second  day 
the  woimd  was  inflamed  and  there  was  slight  ulceration.  It  is  clear 
that  these  later  symptoms  were  due  to  a  secondary  infection.  These 
experiments  have  been  repeated  by  various  observers,  among  whom 
may  be  mentioned  Leon  Dufour,  Josef  Erker  and  Heinzel,  and  with 
the  similar  conclusion  that  the  bite  of  the  ItaHan  tarantula  ordinarily 
causes  no  severe  symptoms.  In  this  conclusion,  Robert,  though 
firmly  convinced  of  the  poisonous  nature  of  some  spiders,  coincides. 
He  also  believes  that  striking  symptoms  may  be  simulated  or  arti- 
ficially induced  by  patients  in  order  to  attract  interest,  or  because 
they  have  been  assured  that  the  bite,  under  all  circiimstances,  caused 
tarantism. 

The  so-called  Russian  tarantula,  Trochosa  singoriensis  (fig.  7),  is 
much  larger  than  the  Italian  species,  and  is  much  feared.  Robert 
carried  out  a  series  of  careful  experiments  with  this  species  and  his 
results  have  such  an  important  bearing  on  the  question  of  the  venom- 
ous nature  of  the  tarantula  that  we  quote  his  summar\\  Experi- 
menting first  on  nearly  a  hundred  living  specimens  of  Trochosa 
singoriensis  from  Crimea  he  says  that: 


Poisonous  Arthropods 


"The  tarantulas,  no  matter  how  often  they  were  placed  on  the 
skin,  handled,  and  irritated,  could  not  be  induced  to  bite  either  myself, 
the  janitor,  or  the  ordinary  experimental  animals.  The  objection 
that  the  tarantulas  were  weak  and  indifferent  cannot  stand,  for  as 
soon  as  I  placed  two  of  them  on  the  shaved  skin  of  a  rabbit,  instead  of 
an  attack  on  the  animal,  there  began  a  furious  battle  between  the 
two  spiders,  which  did  not  cease  until  one  of  the  two  was  killed." 

"Since  the  spiders  would  not 
bite,  I  carefully  ground  up  the 
fresh  animals  in  physiological 
salt  solution,  preparing  an  extract 
which  must  have  contained,  in 
solution,  all  of  the  poisonous 
substance  of  their  bodies.  While 
in  the  case  of  Latrodectus,  as  we 
shall  see,  less  than  one  specimen 
sufficed  to  yield  an  active  extract, 
I  have  injected  the  filtered  extract 
of  six  fresh  Russian  taranttdas, 
of  which  each  one  was  much 
heavier  than  an  average  Latro- 
dectus, subcutaneously  and  into 
the  jugular  vein  of  various  cats 
without  the  animals  dying  or 
showing  any  special  symptoms. 
On  the  basis  of  my  experiments  I  can  therefore  only  say  that  the 
quantity  of  the  poison  soluble  in  physiological  salt  solution,  even 
when  the  spiders  are  perfectly  fresh  and  well  nourished,  is  very 
insignificant.  That  the  poison  of  the  Russian  tarantula  is  not 
soluble  in  physiological  salt  solution,  is  exceedingly  improbable. 
Moreover,  I  have  prepared  alcoholic  extracts  and  was  unable  to 
find  them  active.  Since  the  Russian  spider  exceeds  the  Italian  in 
size  and  in  intensity  of  the  bite,  it  seems  very  improbable  to  me  that 
the  pharmacological  test  of  the  Italian  tarantula  would  yield 
essentially  other  results  than  those  from  the  Russian  species." 

To  the  Avicularoidea  belong  the  largest  and  most  formidable 
appearing  of  the  spiders  and  it  is  not  strange  that  in  the  New  World 
they  have  fallen  heir  to  the  bad  reputation,  as  well  as  to  the  name  of 
the  tarantula  of  Europe.  In  this  country  they  occur  only  in  the 
South  or  in  the  far  West,  but  occasionally  living  specimens  are  brought 


7.     Trochosa  singoriensis.     After  Kobert. 


The  Tarantulas 


13 


to  our  northern  ports  in  shipments  of  bananas  and  other  tropical 
produce,  and  are  the  source  of  much  alarm.  It  should  be  mentioned, 
however,  that  the  large  spider  most  frequently  fotind  under  such  cir- 
cumstances is  not  a  tarantula  at  all,  but  one  of  the  Heteropodida;,  or 
giant  crab-spiders,  (fig.  8). 

In  spite  of  their  prominence  and  the  fear  which  they  arouse  there 
are  few  accurate  data  regarding  these  American  tarantulas.     It  has 


S.      The  giant  crab-spider  or  banana  spider  (.IltteropoJa  venatoria). 
Natural  size.     After  Comstock. 

£)ften  been  shown  experimentally  that  they  can  kill  small  birds  and 
mammals,  though  it  is  doubtful  if  these  form  the  normal  prey  of  any 
of  the  species,  as  has  been  claimed.  There  is  no  question  but  that 
the  mere  mechanical  injury  which  they  may  inflict,  and  the  consequent 
chances  of  secondary  infection,  justify,  in  part,  their  bad  reputation. 
In  addition  to  the  injury  from  their  bite,  it  is  claimed  that  the  body 
hairs  of  several  of  the  South  American  species  are  readily  detached 
and  are  urticating. 

Recently,  Phisalix  (191 2)  has  made  a  study  of  the  physiological 
effects  of  the  venom  of  two  Avicularoidea,  Phormtctopus  carcerides 
Pocock,  from  Haiti  and  Cteniza  sauvagei  Rossi,  from  Corsica.  The 
glands  were  removed  aseptically  and  ground  up  with  fine,  sterilized 
sand  in  distilled  water.  The  resultant  liquid  was  somewhat  viscid, 
colorless,  and  feebly  alkaline.     Injected  into  sparrows  and  mice  the 


14  Poisonous  Arthropods 

extract  of  Phormictopus  proved  very  actively  poisonous,  that  from  a 
single  spider  being  sufficient  to  kill  ten  sparrows  or  twenty  mice.  It 
manifested  itself  first  and,  above  all,  as  a  narcotic,  slightly  lowering 
the  temperature  and  paralyzing  the  respiration.  Muscular  and 
cardiac  weakening,  loss  of  general  sensibility,  and  the  disappearance 
of  reflexes  did  not  occur  until  near  the  end.  The  extract  from  Cteniza 
was  less  active  and,  curiously  enough,  the  comparative  effect  on 
sparrows  and  on  mice  was  just  reversed. 

Spiders  of  the  Genus  Latrodectus. — While  most  of  the  popular 
accounts  of  evil  effects  from  the  bites  of  spiders  will  not  stand  investi- 
gation, it  is  a  significant  fact  that,  the  world  over,  the  best  authentica- 
ted records  refer  to  a  group  of  small  and  comparatively  insignificant 
spiders  belonging  to  the  genus  Latrodectus,  of  the  family  Theridiidse. 
The  dread  "  Malmigniatte"  of  Corsica  and  South  Eiurope,  the  "Kara- 
kurte"  of  southeastern  Russia,  the  "Katipo"  of  New  Zealand  the 
"Mena-vodi"  and  "  Vancoho"  of  Madagascar,  and  our  own  Latrodectus 
mactans,  all  belong  to  this  genus,  and  concerning  all  of  these  the  most 
circumstantial  accounts  of  their  venomous  nature  are  given.  These 
accounts  are  not  mere  fantastic  stories  by  luieducated  natives  but  in 
many  cases  are  reports  from  thoroughly  trained  medical  men. 

The  sjonptoms  produced  are  general,  rather  than  local.  As 
smnmarized  by  Kobert  (1901)  from  a  study  of  twenty-two  cases 
treated  in  1888,  in  the  Kherson  (Russia)  Government  Hospital  and 
Berislaw  (Kherson)  District  Hospital  the  typical  case,  aside  from 
complications,  exhibits  the  following  symptoms.  The  victim  sud- 
denly feels  the  bite,  like  the  sting  of  a  bee.  Swelling  of  the  barely 
reddened  spot  seldom  follows.  The  shooting  pains,  which  quickly 
set  in,  are  not  manifested  at  the  point  of  injury  but  localized  at  the 
joints  of  the  lower  limb  and  in  the  region  of  the  hip.  The  severity 
of  the  pain  forces  the  victim  to  the  hospital,  in  spite  of  the  fact  that 
they  otherwise  have  a  great  abhorrence  of  it.  The  patient  is  unable 
to  reach  the  hospital  afoot,  or,  at  least,  not  without  help,  for  there  is 
usually  inability  to  walk.  The  patient,  even  if  he  has  ridden,  reaches 
the  hospital  covered  with  cold  sweat  and  continues  to  perspire  for  a 
considerable  period.  His  expression  indicates  great  suffering.  The 
respiration  may  be  somewhat  dyspnoeic,  and  a  feeling  of  oppression 
in  the  region  of  the  heart  is  common.  There  is  great  aversion  to 
solid  food,  but  increasing  thirst  for  milk  and  tea.  Retention  of 
urine,   and  constipation  occur.     Cathartics  and,   at  night,   strong 


spiders  of  the  Genus  Latrodectus  15 

narcotics  are  desired.  Warm  baths  give  great  relief.  After  three 
days,  there  is  marked  improvement  and  usually  the  patient  is  dis- 
missed after  the  fifth.  This  summan,'  of  s\TTiptoms  agrees  well  -^-ith 
other  trustworthy  records. 

It  would  seem,  then,  that  Riley  and  Howard  (1889),  who  discussed 
a  number  of  accounts  in  the  entomological  literature,  were  fully 
justified  in  their  statement  that  "It  must  be  admitted  that  certain 
spiders  of  the  genus  Latrodectus  have  the  power  to  inflict  poisonous 
bites,  which  may  (probabh-  exceptionally  and  depending  upon  excep- 
tional conditions)  bring  about  the  death  of  a  htrman  being." 

And  yet,  until  recently  the  evidence  bearing  on  the  question  has 
been  most  conflicting.  The  eminent  arachnologist,  Lucas,  (1843) 
states  that  he  himself,  had  been  repeatedly  bitten  by  the  Malmigniatte 
without  any  bad  effects.  Dr.  Marx,  in  1890,  gave  before  the  Ento- 
mological Society  of  Washington,  an  account  of  a  series  of  experiments 
to  determine  whether  the  bite  of  Latrodectus  mactans  is  poisonous  or 
not.  He  described  the  poison  glands  as  remarkably  small*  and  stated 
that  he  had  introduced  the  poison  in  various  ways  into  guinea-pigs 
and  rabbits  -wdthout  obtaining  an}^  satisfacton,'  results.  Obviously, 
carefully  conducted  experiments  mth  the  supposed  venom  were 
needed  and  fortunately  they  have  been  carried  out  in  the  greatest 
detail  by  Kobert  (190 1). 

This  investigator  pointed  out  that  there  were  two  factors  which 
might  account  for  the  discrepancies  in  the  earlier  experiments.  In 
the  first  place,  the  poison  of  spiders,  as  of  snakes,  might  be  so  ex- 
hausted after  two  or  three  bites  that  further  bites,  following  directly, 
might  be  without  \'isible  effect.  Secondly,  the  application  of  the 
poison  by  means  of  the  bite,  is  exceedingly  inexact,  since  even  after 
the  most  careful  selection  of  the  point  of  application,  the  poison  might 
in  one  instance  enter  a  little  vein  or  lymph  vessel,  and  in  another  case 
fail  to  do  so.  Besides,  there  would  always  remain  an  incalculable  and 
very  large  amount  externally,  in  the  nonabsorptive  epithelium. 
While  all  of  these  factors  enter  into  the  question  of  the  effect  of  the 
bite  in  specific  instances,  they  must  be  as  nearly  as  possible  obviated 
in  considering  the  question  of  whether  the  spiders  really  secrete  a 
venom  harmful  to  man. 


*This  is  diametrically  opposed  to  the  findings  of  Bordas  (1905)  in  the  case 
of  the  European  Latrodectus  ij-guttatus,  whose  glands  are  "much  larger  than 
those  of  other  spiders."  From  a  considerable  comparative  study,  we  should  also 
unhesitatingly  make  this  statement  regarding  the  glands  of  our  American  species, 
L.  mactans. 


1 6  Poisonous  Arthropods 

Robert  therefore  sought  to  prepare  extracts  which  would  contain 
the  active  principles  of  the  poison  and  which  could  be  injected  in 
definite  quantities  directly  into  the  blood  of  the  experimental  animal. 
For  this  purpose  various  parts  of  the  spiders  were  rubbed  up  in  a  mor- 
tar with  distilled  water,  or  physiological  salt  solution,  allowed  to 
stand  for  an  hour,  filtered,  and  then  carefully  washed,  by  adding  water 
drop  by  drop  for  twenty-four  hours.  The  filtrate  and  the  wash- 
water  were  then  united,  well  mixed  and,  if  necessary,  cleared  by  cen- 
trifuging  or  by  exposure  to  cold.  The  mixture  was  again  filtered, 
measured,  and  used,  in  part,  for  injection  and,  in  part,  for  the  deter- 
mination of  the  organic  materials. 

Such  an  extract  was  prepared  from  the  cephalothoraces  of  eight 
dried  specimens  of  the  Russian  Latrodectus  and  three  cubic  centimeters 
of  this,  containing  4.29  mg.  of  organic  material,  were  injected  into 
the  jugular  vein  of  a  cat  weighing  2450  grams.  The  previously  very 
active  animal  was  paralyzed  and  lay  in  whatever  position  it  was 
placed.  The  sensibility  of  the  skin  of  the  extremities  and  the  rump 
was  so  reduced  that  there  was  no  reaction  from  cutting  or  sticking. 
There  quickly  followed  dyspnoea,  convulsions,  paralysis  of  the 
respiratory  muscles  and  of  the  heart.  In  twenty-eight  minutes  the 
cat  was  dead,  after  having  exhibited  exactly  the  symptoms  observed 
in  severe  cases  of  poisoning  of  man  from  the  bite  of  this  spider. 

These  experiments  were  continued  on  cats,  dogs,  guinea  pigs  and 
various  other  animals.  Not  only  extracts  from  the  cephalothorax, 
but  from  other  parts  of  the  body,  from  newly  hatched  spiders,  and 
from  the  eggs  were  used  and  all  showed  a  similar  virulence.  Every 
effort  was  made  to  avoid  sources  of  error  and  the  experiments,  con- 
ducted by  such  a  recognized  authority  in  the  field  of  toxicology,  must 
be  accepted  as  conclusively  showing  that  this  spider  and,  presimiably, 
other  species  of  the  genus  Latrodectus  against  which  the  clinical  evi- 
dence is  quite  parallel,  possess  a  poison  which  paralyzes  the  heart  and 
central  nervous  system,  with  or  without  preliminary  stimulus  of  the 
motor  center.  If  the  quantity  of  the  poison  which  comes  into  direct 
contact  with  the  blood  is  large,  there  may  occur  haemolysis  and 
thrombosis  of  the  vessels. 

On  1he  other  hand,  check  experiments  were  carried  out,  using 
similar  extracts  of  many  common  European  spiders  of  the  genera 
Tegenaria,  Drassus,  Agelena,  Eucharia  and  Argyroneta,  as  well  as 
the  Russian  tarantula,  Lycosa  singoriensis.  In  no  other  case  was  the 
effect  on  experimental  animals  comparable  to  the  Latrodectus  extract. 


spiders  of  the  Genus  Latrodectus 


17 


Robert  concludes  that  in  its  chemical  nature  the  poison  is  neither 
an  alkaloid,  nor  a  glycoside,  nor  an  acid,  but  a  toxalbumen,  or  poison- 
ous enz}Tne  which  is  very  similar  to  certain  other  animal  poisons, 
notably  that  of  the  scori)ion. 


9.     Latrodectus  mactans 


(a)  female,  X  3;    (b)  venter  of  female;    (c)  dorsum  of  male. 
After  Comstock. 


The  genus  Latrodectus  is  represented  in  the  United  States  by  at 
least  two  species,  L.  mactans  and  L.  geometricus.  Concerning  L. 
mactans  there  are  very  circiimstantial  accounts  of  serious  injury  and 
even  death  in  man*.  Latrodectus  mactans  \s  coal  black,  marked  with 
red  or  yellow  or  both.      It  has  eight  eyes,  which  are  dissimilar  in 


*Dr.  E.  H.  Coleman  (Kellogg,  1915)  has  demonstrated  its  virulence  by  a  series 
of  experiments  comparable  with  those  of  Kobert. 


1 8  Poisonous  Arthropods 

color  and  are  distinctly  in  front  of  the  middle  of  the  thorax,  the 
lateral  eyes  of  each  side  widely  separate.  The  tarsi  of  the  fourth 
pair  of  legs  has  a  ntunber  of  curved  setae  in  a  single  series.  It  has  on 
the  ventral  side  of  its  abdomen  an  hour-glass  shaped  spot.  The  full- 
grown  female  is  about  half  an  inch  in  length.  Its  globose  abdomen  is 
usually  marked  with  one  or  more  red  spots  dorsally  along  the  middle 
line.  The  male  is  about  half  as  long  but  has  in  addition  to  the  dorsal 
spots,  four  pairs  of  stripes  along  the  sides.  Immature  females 
resemble  the  male  in  coloring  (fig.  9). 

Regarding  the  distribution  of  Latrodectus  mac  tans,  Comstock 
states  that:  "Although  it  is  essentially  a  Southern  species,  it  occurs 
in  Indiana,  Ohio,  Pennsylvania,  New  Hampshire,  and  doubtless  other 
of  the  Northern  States."  L.  geometricus  has  been  reported  from 
California. 

Other  Venomous  Spiders — While  conclusive  evidence  regarding 
the  venomous  nature  of  spiders  is  meager  and  relates  almost  wholly 
to  that  of  the  genus  Latrodectus,  the  group  is  a  large  one  and  we  are 
not  justified  in  dismissing  arbitrarily,  all  accounts  of  injury  from  their 
bites.  Several  species  stand  out  as  especially  needing  more  detailed 
investigation. 

Chiracanthium  nutrix  is  a  common  European  species  of  the  family 
Clubionidse,  concerning  which  there  is  much  conflicting  testimony. 
Among  the  reports  are  two  by  distinguished  scientists  whose  accounts 
of  personal  experiences  cannot  be  ignored.  A.  Forel  allowed  a  spider 
of  this  species  to  bite  him  and  not  only  was  the  pain  extreme,  but  the 
general  symptoms  were  so  severe  that  he  had  to  be  helped  to  his 
house.  The  distinguished  arachnologist,  Bertkau  reports  that  he, 
himself,  was  bitten  and  that  an  extreme,  burning  pain  spread  almost 
instantaneously  over  the  arm  and  into  the  breast.  There  were  slight 
chills  the  same  day  and  throbbing  pain  at  the  wound  lasted  for  days. 
While  this  particiilar  species  is  not  found  in  the  United  States,  there 
are  two  other  representatives  of  the  genus  and  it  is  possible  that  they 
possess  the  same  properties.  We  are  unaware  of  any  direct  experi- 
mental work  on  the  poison. 

Epeira  diadema,  of  Europe,  belongs  to  a  wholly  different  group, 
that  of  the  orb-weavers,  but  has  long  been  reputed  venomous.  Kobert 
was  able  to  prepare  from  it  an  extract  whose  effects  were  very  similar 
to  that  prepared  from  Latrodectus,  though  feebler  in  its  action.  Under 
ordinary  circumstances  this  spider  is  unable  to  pierce  the  skin  of  man 


Other  Venomous  Spiders 


19 


and  though  Kobcrt's  results  seem  conclusive,  the  spider  is  little  to 
be  feared. 

Phidipptis  audax  (P.  tripunctatus)  is  one  of  our  largest  Attids, 
or  jumping  spiders.  The  late  Dr.  O.  Lugger  describes  a  case  of  severe 
poisoning  from  the  bite  of  this  spider  and  though  details  are  lacking, 
it  is  quite  possible  that  this  and  other  large  species  of  the  same  group, 
which  stalk  their  prey,  may  possess  a  more  active  poison  than  that  of 
web-building  species. 

Summary — It  is  clearly  estabhshed  that  our  common  spiders  are 
not  to  be  feared  and  that  the  stories  regarding  their  virulence  are 

almost  wholly  without  founda- 
tion. On  the  other  hand,  the 
chances  of  secondary  infection 
from  the  bites  of  some  of  the 
more  powerful  species  are  not 
to  be  ignored. 

Probably  all  species  possess 
a  toxin  secreted  by  the  poison 
gland,  virulent  for  insects  and 
other  normal  prey  of  the 
spiders,  but  with  little  or  no 
effect  on  man. 

There  are  a  very  few  species, 
notably  of  the  genus  Latrodectus, 
and  possibly  including  the  Euro- 
pean Chiracanthium  nutrix  and 
Epeira  diadema,  which  possess, 
in  addition,  a  toxalbumen 
10.   A  whip-scorpion  (Mattigoproctus  giganteus).  dcrivcd  from  the  general  body 

Half  natural  size.      After  Comstock.  .•  1  •    -u  •        r  ^     •       1 

tissue,  which  is  of  great  virulence 
and  ma\'  even  cause  death  in  man  and  the  higher  animals. 

TKE   PEDIPALProA   OR  WHIP-SCORPIONS 

The  tailed  whip-scorpions,  belonging  to  the  family  Thelyphonidae, 
are  represented  in  the  United  States  by  the  giant  whip-scorpion 
Mastigopr actus  giganteus  (fig.  lo),  which  is  common  in  Florida,  Texas 
and  some  other  parts  of  the  South.  In  Florida,  it  is  locally  known  as 
the  "grampus"  or  "mule-killer"  and  is  very  greatly  feared.  There  is 
no  evidence  that  these  fears  have  any  foundation,  and  Dr.  Marx 
states  that  there  is  neither  a  poison  gland  nor  a  pore  in  the  claw  of  the 
chelicera. 


Poisonous  Arthropods 


THE  SCORPIONroA,  OR  TRUE   SCORPIONS 

The  true  scorpions  are  widely  distributed  throughout  warm  coun- 
tries and  everywhere  bear  an  evil  reputation .  According  to  Comstock 
(19 1 2),  about  a  score  of  species  occur  in  the  Southern  United  States. 
These  are  comparatively  small  forms  but  in  the  tropics  members  of 
this  group  may  reach  a  length  of  seven  or  eight  inches.  They  are 
pre-eminently  predaceous  forms,  which  lie  hidden  during  the  day  and 
seek  their  prey  by  night. 

The  scorpions  (fig.  11)  possess  large  pedipalpi,  terminated  by 
strongly  developed  claws,  or  chelae.  They  may  be  distinguished  from 
all  other  Arachnids  by  the  fact  that  the  dis- 
tinctly segmented  abdomen  is  divided  into  a 
broad  basal  region  of  seven  segments  and  a 
terminal,  slender,  tail-like  division  of  five 
distinct  segments. 

The  last  segment  of  the  abdomen,  or 
telson,  terminates  in  a  ventr ally-directed, 
sharp  spine,  and  contains  a  pair  of  highly 
developed  poison  glands.  These  glands  open 
by  two  small  pores  near  the  tip  of  the  spine. 
Most  of  the  species  when  running  carry  the 
tip  of'  the  abdomen  bent  upward  over  the 
back,  and  the  prey,  caught  and  held  by  the 
pedipalpi,  is  stung  by  inserting  the  spine  of 
the  telson  and  allowing  it  to  remain  for  a 
time  in  the  wound. 

The  glands  themselves  have  been  studied 
in  Prionurus  citrinus  by  Wilson  (1904). 
He  found  that  each  gland  is  covered  by  a  sheet  of  muscle  on  its 
mesal  and  dorsal  aspects,  which  may  be  described  as  the  compressor 
muscle.  The  muscle  of  each  side  is  inserted  by  its  edge  along  the 
ventral  inner  surface  of  the  chitinous  wall  of  the  telson,  close  to  the 
middle  line,  and  by  a  broader  insertion  laterally.  A  layer  of  fine 
connective  tissue  completely  envelops  each  gland  and  forms  the 
basis  upon  which  the  secreting  cells  rest.  The  secreting  epithelium 
is  coliminar;  and  apparently  of  three  different  types  of  cells. 

I.  The  most  numerous  have  the  appearance  of  mucous  cells, 
resembling  the  goblet  cells  of  columnar  mucous  membranes.  The 
nucleus,  surroimded  by  a  small  quantity  of  protoplasm  staining  with 
haematoxylin,  lies  close  to  the  base  of  the  cell. 


A  true    scorpion. 
Comstock. 


After 


The  True  Scorpions  21 

2.  Cells  present  in  considerable  numbers,  the  peripheral  por- 
tions of  which  are  filled  with  very  numerous  fine  granules,  staining 
with  acid  dyes  such  as  methyl  orange. 

3.  Cells  few  in  number,  filled  with  very  large  granules,  or  ir- 
regular masses  of  a  substance  staining  mth  hcematoxylin. 

The  poison,  according  to'  Robert  (1893),  is  a  limpid,  acid-reacting 
fluid,  soluble  in  water  but  insoluble  in  absolute  alcohol  and  ether. 
There  are  few  data  relative  to  its  chemical  nature.  Wilson  (1901) 
states  that  a  common  Egyptian  species,  Buthus  qMinquestriatus, "has 
a  specific  gravity  of  1.092,  and  contains  20.3%  of  solids  and  8.4%  ash. 

The  venom  of  different  species  appears  to  differ  not  only  quantita- 
tivel}'  but  qualitatively.  The  effects  of  the  bite  of  the  smaller  species 
of  the  Southern  United  States  may  be  painful  but  there  is  no  satis- 
factory- evidence  that  it  is  ever  fatal.  On  the  other  hand,  certain 
tropical  species  are  exceedingh'-  virulent  and  cases  of  death  of  man 
from  the  bite  are  common. 

In  the  case  of  Buthus  quinquestriatus ,  Wilson  (1904)  found  the 
symptoms  in  animals  to  be  hypersecretion,  salivation  and  lachryma- 
tion,  especially  marked,  convulsions  followed  by  prolonged  mus- 
ciilar  spasm;  death  from  asphyxia.  The  temperature  shows  a 
slight,  rarely  considerable,  rise.  Rapid  and  considerable  increase 
of  blood-pressure  (observed  in  dogs)  is  followed  by  a  gradual  fall  with 
slo^ving  of  the  heart-beat.  The  coagulability  of  the  blood  is  not 
affected. 

An  interesting  phase  of  Wilson's  work  was  the  experiments  on 
desert  mammals.  The  condition  under  which  these  animals  exist 
must  frequently  bring  them  in  contact  with  scorpions,  and  he  found 
that  they  possess  a  degree  of  immunity  to  the  venom  sufficient  at 
least  to  protect  them  from  the  fatal  effects  of  the  sting. 

As  far  as  concerns  its  effect  on  man,  Wilson  foimd  that  much 
depended  upon  the  age.  As  high  as  60  per  cent  of  the  cases  of 
children  under  five,  resulted  fatally.  Caroroz  (1865),  states  that  in  a 
Mexican  state  of  15,000  inhabitants,  the  scorpions  were  so  abundant 
and  so  much  feared  that  the  authorities  offered  a  bounty  for  their 
destruction.  A  result  was  a  large  number  of  fatahties,  over  two 
hundred  per  year.  Most  of  the  victims  were  children  who  had 
attempted  to  collect  the  scorpions. 

The  treatment  usually  employed  in  the  case  of  bites  by  the  more 
poisonous  forms  is  similar  to  that  for  the  bite  of  venomous  snakes. 
First,  a  tight  ligature  is  applied  above  the  wound  so  as  to  stop  the 


22  Poisonous  Arthropods 

flow  of  blood  and  lymph  from  that  region.  The  wound  is  then 
freely  excised  and  treated  with  a  strong  solution  of  permanganate 
of  potash,  or  with  lead  and  opium  lotion. 

In  recent  years  there  have  been  many  attempts  to  prepare  an 
antivenom,  or  antiserum  comparable  to  what  has  been  used  so 
effectively  in  the  case  of  snake  bites.  The  most  promising  of  these 
is  that  of  Todd  (1909),  produced  by  the  immunization  of  suitable 
animals.  This  antivenom  proved  capable  of  neutralizing  the  venom 
when  mixed  in  vitro  and  also  acts  both  prophylactically  and  cura- 
tively  in  animals.  Employed  curatively  in  man,  it  appears  to  have 
a  very  marked  effect  on  the  intense  pain  following  the  sting,  and 
the  evidence  so  far  indicates  that  its  prompt  use  greatly  reduces 
the  chance  of  fatal  results. 


THE   SOLPUOroA,  OR  SOLPUGmS 

The  Solpugida  are  peculiar  spider-like  forms  which  are  distin- 
guished from  nearly  all  other 
Hs^///.  \\ll!^/  arachnids  by   the   fact   that 

they  possess  no  true  cephalo- 
thorax,  the  last  two  leg-bear- 
ing segments  being  distinct, 
resembling  those  of  the  abdo- 
men in  this  respect.  The 
first  pair  of  legs  is  not  used 
in  locomotion  but  seemingly 
functions  as  a  second  pair  of 
pedipalpi.  Figure  12  illus- 
trates the  striking  peculiari- 
ties of  the  group.  They  are 
primarily  desert  forms  and 
occur  in  the  warm  zones  of 
all  countries.  Of  the  two 
hundred  or  more  species, 
Comstock  lists  twelve  as 
occurring  in  our  fauna. 
These  occur  primarily  in  the 
southwest. 

The  Solpugida  have  long 
borne  a  bad  reputation  and  regarding  virulence,  have  been  classed 
with   the  scorpions.     Among  'the  effects  of  their  bites  have  been 


A  solpugid  (Eremobates  cinerea). 
stock. 


After  Com- 


Mites  and  Ticks  23 

described  painful  swelling,  gangrene,  loss  of  speech,  cramps,  deliri- 
um, unconsciousness  and  even  death.  Opposed  to  the  numerous  loose 
accounts  of  poisoning,  there  are  a  number  of  careful  records  by 
physicians  and  zoologists  which  indicate  clearly  that  the  effects  are 
local  and  though  they  may  be  severe,  they  show  not  the  slightest 
symptom  of  direct  poisoning. 

More  important  in  the  consideration  of  the  question  is  the  fact 
that  there  are  neither  poison  glands  nor  pores  in  the  fangs  for  the 
exit  of  any  poisonous  secretion.  This  is  the  testimony  of  a  number 
of  prominent  zoologists,  among  whom  is  Dr.  A.  Walter,  who  wrote 
to  Kobert  at  length  on  the  subject  and  whose  conclusions  are  pre- 
sented by  him. 

However,  it  should  be  noted  that  the  fangs  are  very  powerful 
and  are  used  in  such  a  manner  that  they  may  inflict  especially  severe 
wounds.  Thus,  there  may  be  more  opportunity  for  secondary 
infection  than  is  usual  in  the  case  of  insect  wounds. 

The  treatment  of  the  bite  of  the  Solpugida  is,  therefore,  a  matter 
of  preventing  infection.  The  wound  should  be  allowed  to  bleed 
freely  and  then  washed  out  with  a  1 13000  solution  of  corrosive 
sublimate,  and,  if  severe,  a  wet  dressing  of  this  should  be  applied. 
If  infection  takes  place,  it  should  be  treated  in  the  usual  man- 
ner, regardless  of  its  origin. 

THE  ACARINA,  OR  MITES  AND  TICKS 

A  number  of  the  parasitic  Acarina  e\ndently  secrete  a 
specific  poison,  prestmiably  carried  by  the  saliva,  but  in  most  cases 
its  effect  on  man  is  insignificant.  There  is  an  abundant  literature 
dealing  with  the  poisonous  effect  of  the  bite  of  these  forms,  especially 
the  ticks,  but  until  recently  it  has  been  confused  by  failure  to  recog- 
nize that  various  species  may  transmit  diseases  of  man,  rather  than 
produce  injury  through  direct  poisoning.  We  shall  therefore 
discuss  the  Acarina  more  especially  in  subsequent  chapters,  dealing 
with  parasitism  and  with  disease  transmission. 

Nevertheless,  after  the  evidence  is  sifted,  there  can  be  no  doubt 
that  the  bites  of  certain  ticks  may  occasionally  be  followed  by  a 
direct  poisoning,  which  may  be  either  local  or  general  in  its  effects. 
Nuttall  (1908)  was  unable  to  determine  the  cause  of  the  toxic  effect, 
for,  in  Argas  persicus,  the  species  most  often  implicated,  he  failed  to 
get  the  slightest  local  or  general  effect  on  experimental  animals,  from 
the  injection  of  an  emulsion  prepared  by  crushing  three  of  the  ticks. 


24  Poisonous  Arthropods 

It  seems  clearly  established  that  the  bite  of  certain  ticks  may 
cause  a  temporary  paralysis,  or  even  complete  paralysis,  involving 
the  organs  of  respiration  or  the  heart,  and  causing  death.  In  191 2, 
Dr.  I.  U.  Temple,  of  Pendleton,  Oregon,  reported  several  cases  of 
what  he  called  "acute  ascending  paralysis"  associated  with  the  occur- 
rence of  ticks  on  the  head  or  the  back  of  the  neck.  A  typical  severe 
case  was  that  of  a  six  year  old  child,  who  had  retired  in  her  usual 
normal  health.  The  following  morning  upon  arising  she  was  unable 
to  stand  on  her  feet.  She  exhibited  paralysis  extending  to  the  knees, 
slight  temperature,  no  pain,  sensory  ner\^es  normal,  motor  nerves 
completely  parah'zed,  reflexes  absent.  The  following  day  the  paral- 
ysis had  extended  to  the  upper  limbs,  and  before  night  of  the  third 
day  the  nerv^es  of  the  throat  (hypoglossal)  were  affected.  The  thorax 
and  larynx  were  involved,  breathing  was  labored,  she  was  unable 
to  swallow  liquids,  phonation  was  impossible  and  she  could  only  make 
low,  gutteral  sounds.  At  this  stage,  two  ticks,  fully  distended  with 
blood,  were  found  over  the  junction  of  the  spinal  column  with  the 
occipital  bones  in  the  hollow  depression.  They  were  removed  by 
the  application  of  undiluted  creoline.  Though  the  child's  life  was 
despaired  of,  by  the  following  morning  she  was  very  much  improved. 
By  evening  she  was  able  to  speak.  The  paralysis  gradually  receded, 
remaining  longest  in  the  feet,  and  at  the  end  of  one  week  the  patient 
was  able  to  go  home. 

There  was  some  doubt  as  to  the  exact  species  of  tick  implicated 
in  the  cases  which  Dr.  Temple  reported,  although  the  evidence 
pointed  strongly  to  Dermacentor  venustus*  Somewhat  later.  Hadwen 
(19 1 3)  reported  that  "tick  paralysis"  occurs  in  British  Columbia, 
where  it  affects  not  only  man,  but  sheep  and  probably  other  animals. 
It  is  caused  by  the  bites  of  Dermacentor  venustus  and  was  experi- 
mentally produced  in  lambs  and  a  dog  (Hadwen  and  Nuttall,  19 13). 
It  is  only  when  the  tick  begins  to  engorge  or  feed  rapidly,  some  days 
after  it  has  become  attached,  that  its  saliva  produces  pathogenic 
effects. 

Ulceration  following  tick  bite  is  not  uncommon.  In  many  of  the 
instances  it  is  due  to  the  file-like  hypostome,  with  its  recurved  teeth, 
being  left  in  the  wound  when  the  tick  is  forcibly  pulled  off. 


*Accordmg  to  Stiles,  the  species  occurring  in  the  Northwest  which  is  commonly 
identified  as  D.  venustus  should  be  called  D.  andersonii  (see  footnote,  chapter  12). 


Centipedes  and  Millipedes 


25 


^^ 


THE  MYRIAPODA,  OR  CENTIPEDES  AND  MILLIPEDES 

The  old  class,  Myriapoda  includes  the  Diplopoda,  or 
millipedes,  and  the  Chilopoda,  or  centipedes.  The  pres- 
ent tendency  is  to  raise  these  groups  to  the  rank  of 
classes. 

The  Diplopoda 

The  Diplopoda,  or  millipedes  (fig.  13),  are  character- 
ized by  the  presence  of  two  pairs  of  legs  to  a  segment. 
The  largest  of  our  local  myriapods  belong  to  this  group. 
They  live  in  moist  places,  feeding  primarily  on  decay- 
ing vegetable  matter,  though  a  few  species  occasion- 
ally attack  growing  plants. 

The  millipedes  are  inoffensive  and  harmless.  Julus 
terrestris,  and  related  species,  when  irritated  pour  out 
over  the  entire  body  a  yellowish  secretion  which  escapes 
from  cutaneous  glands.  It  is 
volatile,  with  a  pungent  odor, 
and  Phisalix  (1900)  has  shown 
that  it  is  an  active  poison  when 
itte^  Comst^od^  injectcd  into  the  blood  of  experi- 
mental animals.  This,  how- 
ever, does  not  entitle 
them  to  be  considered 
as  poisonous  arthro- 
pods, in  the  sense  of  this 
chapter,  any  more  than 
the  toad  can  be  con- 
sidered poisonous  to 
man  because  it  secretes 
a  venom  from  its  cuta- 
neous glands. 

The  Chilopoda 

The  Chilopoda,'  or 
centipedes  (fig.  14),  un- 
like the  millipedes,  are 
predaceous  forms,  and 
possess  well  developed 

poison    glands    for   kill-  l*-     'J^^°  common  centipedes. 

• J  r.    •  rr^-,  (a)  Lithobius  forficatus.  (6)  Scutigera  forceps.     Natural 

mg   tneir   prey.       These  After  Comstock.  size;  after  Howard. 


2  6  Poisonous  Arthropods 

glands  are  at  the  base  of  the  first  pair  of  legs  (fig.  15),  which  are 
bent  forward  so  as  to  be  used  in  holding  their  prey.  The  legs 
terminate  in  a  powerful  claw,  at  the  tip  of  which  is  the 
outlet  of  the  poison  glands. 

The  poison  is  a  limpid,  homogeneous,  slightly  acid 
fluid,  which  precipitates  in  distilled  water.  Briot  (1904) 
extracted  it  from  the  glands  of  Scolopendra  morsitans,  a 
species  common  in  central  France,  and  found  that  it  was 
actively  venomous  for  the  ordinary  experimental  ani- 
mals. A  rabbit  of  two  kilograms  weight  received  an 
15  Mandible  of  i^j^ction  of  thrcc  cubic  centimeters  in  the  vein  of  the  ear 
Scolopendra  ^nd  died  in  a  minute.     A  white  rat,  weighing  forty-eight 

cmgulata  >  &         &  j        b 

showing  prrams,  received  one  and  a  half  cubic  centimeters  in  the 

V   e  n    o  m     ° 

Dubo-  ^^^^  hind  leg.  There  was  an  almost  immediate  paralysis  of 
the  leg  and  marked  necrosis  of  the  tissues. 

As  for  the  effect  on  man,  there  is  little  foundation  for  the  fear 
with  which  centipedes  are  regarded.  Our  native  species  produce, 
at  most,  local  symptoms, — sometimes  severe  local  pain  and  swell- 
ing,— but  there  is  no  authentic  record  of  fatal  results.  In  the  tropics, 
some  of  the  species  attain  a  large  size,  Scolopendra  gigantea  reaching 
a  length  of  nearly  a  foot.  These  forms  are  justly  feared,  and  there 
is  good  evidence  that  death  sometimes,  though  rarely,  results  from 
their  bite. 

One  of  the  most  careful  accounts  of  death  from  the  sting  of  the 
scorpion  is  that  of  Linnell,  (1914),  which  relates  to  a  comparatively 
small  Malayan  species,  unfortunately  undetermined.  The  patient, 
a  coolie,  aged  twenty,  was  admitted  to  a  hospital  after  having  been 
stung  two  days  previously  on  the  left  heel.  For  cure,  the  other 
coolies  had  made  him  eat  the  head  of  the  scorpion.  On  admission, 
the  patient  complained  of  "things  creeping  all  over  the  body". 
Temp.  102.8°.  On  the  fourth  day  he  had  paralysis  of  the  legs,  and 
on  the  fifth  day  motor  paralysis  to  the  umbilicus,  sensation  being 
unaltered.  On  the  sixth  day  there  was  retention  of  the  urine  and 
on  the  ninth  day  (first  test  after  third  day)  sugar  was  present.  On 
the  thirteenth  day  the  patient  became  comatose,  but  could  be 
roused  to  eat  and  drink.  The  temperature  on  the  following  day  fell 
below  95°  and  the  patient  was  still  comatose.     Death  fifteenth  day. 

Examination  of  the  spinal  (lumbar)  cord  showed  acute  dissemi- 
nated myelitis.  In  one  part  there  was  an  acute  destruction  of  the 
anterior  horn  and  an  infiltration  of  round  cells.     In  another  portion 


Hexapoda,  or  True  Insects  27 

Clarke's  column  had  been  destroyed.  The  perivascular  sheaths 
were  crowded  with  small  round  cells  and  the  meninges  were  con- 
gested. Some  of  the  cells  of  the  anterior  horn  were  swollen  and  the 
nuclei  eccentric;   chromatolysis  had  occurred  in  many  of  them. 

As  for  treatment,  Castellani  and  Chalmers  (19 10),  recommend 
bathing  the  part  well  with  a  solution  of  ammonia  (one  in  five,  or  one 
in  ten).  After  bathing,  apply  a  dressing  of  the  same  alkali  or,  if 
there  is  much  swelling  and  redness,  an  ice-bag.  If  necessary,  hypo- 
dermic injections  of  morphine  may  be  given  to  relieve  the  pain. 
At  a  later  period  fomentations  may  be  required  to  reduce  the  local 
inflammation. 

THE  HEXAPODA  OR  TRUE  INSECTS 

There  are  a  nimiber  of  Hexapoda,  or  true  insects,  which  are,  in 
one  way  or  another,  poisonous  to  man.  These  belong  primarily 
to  the  orders  Hemiptera,  or  true  bugs;  Lepidoptera,  or  butterflies 
and  moths  (larval  forms);  Diptera,  or  flies;  Coleoptera,  or  beetles; 
and  Hymenoptera,  or  ants,  bees,  and  wasps.  There  are  various  ways 
in  which  they  may  be  poisonous. 

1.  Piercing  or  biting  forms  may  inject  an  irritating  or  poisonous 
sali^"a  into  the  wound  caused  by  their  mouth-parts. 

2.  Stinging  forms  may  inject  a  poison,  from  glands  at  the  caudal 
end  of  the  abdomen,  into  wounds  produced  by  a  specially  modified 
ovipositer,  the  sting. 

3 .  Nettling  properties  may  be  possessed  by  the  hairs  of  the  insect. 

4.  Vescicating,  or  poisonous  blood  plasma,  or  body  fluids  are 
known  to  exist  in  a  large  number  of  species  and  may,  under  excep- 
tional circumstances,  affect  man. 

For  convenience  of  discussion,  we  shall  consider  poisonous  insects 
under  these  various  headings.  In  this,  as  in  the  preceding  discussion, 
no  attempt  will  be  made  to  give  an  exhaustive  list  of  the  poisonous 
forms.  Typical  instances  will  be  selected  and  these  will  be  chosen 
largely  from  North  American  species. 

PIERCING  OR  BITING  INSECTS  POISONOUS  TO  MAN 

Hemiptera 

Several  families  of  the  true  bugs  include  forms  which,  while 
normally  inoffensive,  are  capable  of  inflicting  painful  wounds  on  man. 
In  these,  as  in  all  of  the  Hemiptera,  the  mouth-parts  are  modified 


28 


Poisonous  Arthropods 


Muick  of  pump  — '■^ 


•l.ahrwni 


^  <5heathi'  labium 
-*SeLa£-,-»  ^fandtble  and  ^foxi^/oc 


Beak  of  hemipteron. 


to  form  an  organ  for  piercing  and 
sucking.  This  is  well  shown  by  the 
accompanying  illustration  (fig.  i6). 
The  upper  lip,  or  labrum ,  is  much 
reduced  and  immovable,  the  lower 
lip,  or  labium,  is  elongated  to  form 
a  jointed  sheath,  within  which  the 
lance-like  mandibles  and  maxillae 
are  enclosed.  The  mandibles  are 
more  or  less  deeply  serrate,  depend- 
ing on  the  species  concerned. 
The  poison  is  elaborated  by  the  salivary  glands,  excepting,  possi- 
bly, in  Belostoma  where  Locy  is  inclined  to  believe  that  it  is  secreted 
by  the  maxillary  glands.  The  salivary  glands 
of  the  Hemiptera  have  been  the  subject  of 
much  study  but  the  most  recent,  comprehen- 
sive^work  has  been  done  by  Bugnion  and  Popoff, 
(1908  and  1 9 10)  to  whose  text  the  reader  is 
referred  for  details. 

The  Hemiptera  have  two 
pairs  of  salivary  glands :  the 
primary  gland,  of  which  the 
efferent  duct  leads  to  the 
salivary  syringe,  and  the 
accessory  gland,  of  which  the 
very  long  and  flexuous  duct 
empties  into  the  primary  duct 
at  its  point  of  insertion. 
Thus,  when  one  observes  the 
isolated  primary  gland  it  appears  as  though  it 
had  efferent  ducts  inserted  at  the  same  point.  In 
Nepa  and  the  Fulgoridcs  there  are  two  accessory 
glands  and  therefore  apparenth^  three  ducts 
at  the  same  point  on  the  primary  gland.  The 
ensemble  differs  greatly  in  appearance  in  different 
species  but  we  shall  show  here  Bugnion  and 
Popoff's  figure  of  the  apparatus  of  Notonecta 
^^'  s^HvTr^^pump'^LTFuT  '^^cLCulata,  d.  specics  capable  of  inflicting  a  painful 
&rn\td%^r  bite  on  man  (fig.  17). 


17. 


Salivary  glands  of 
Notonecta  maculata. 
After  Bugnion  and 
Popoff. 


Hemiptera,  or  True  Bugs 


29 


Accessory  to  the  salivary  apparatus  there  is  on  the  ventral  side 
of  the  head,  underneath  the  pharynx,  a  peculiar  organ  which  the 


19.  Heteroptera,  (a)  Melanolestes  picipes;  (b)  Notonecta  undulata;  (c.d)  Aradus  robustus 
(c)  adult,  (d)  nymph,  much  enlarged;  (e)  Arilus  cristatus;  (/)  Belostoma  americana; 
(g)  Nabis  (Coriscus)  subcoleoptratus,  enlarged;  (/»)  Cimex  lectularius,  (»)  Oeciacus 
vicarius,  much  enlarged;    (j)  Lyctocoris  fitchii,  much  enlarged      After  Lugger. 


Germans  have  called  the  "  Wanzenspritze,"  or  syringe.  The  ac- 
companying figure  of  the  structure  in  Fulgora  maculata  (fig.  18)  shows 
its  relation  to  the  ducts  of  the  salivary  glands  and  to  the  beak.     It  is 


30  Poisonous  Arthropods 

made  up  of  a  dilatation  forming  the  body  of  the  pump,  in  which  there 
is  a  chitinous  piston.  Attached  to  the  piston  is  a  strong  retractor 
muscle.  The  function  of  the  sahvary  pump  is  to  suck  up  the  saliva 
from  the  salivary  ducts  and  to  force  it  out  through  the  beak. 

Of  the  Hemiptera  reported  as  attacking  man,  we  shall  consider 
briefly  the  forms  most  frequently  noted. 

The  Notonectidae,  or  hack  swimmers,  (fig.  196)  are  small,  aquatic 
bugs  that  differ  from  all  others  in  that  they  always  swim  on  their 
backs.  They  are  predaceous,  feeding  on  insects  and  other  small 
forms.  When  handled  carelessly  they  are  able  to  inflict  a  painful . 
bite,  which  is  sometimes  as  severe  as  the  sting  of  a  bee.  In  fact, 
they  are  known  in  Germany  as  "  Wasserbienen." 

The  Belostomatidae,  or  giant  water  bugs,  (fig.  19/)  include  the  largest 
living  Hemiptera.  They  are  attracted  to  lights  and  on  account  of  the 
large  numbers  which  swarm  about  the  electric  street  lamps  in  some 
localities  they  have  deceived  the  popular  name  "electric  light  bugs." 
Our  largest  representatives  in  the  northern  United  States  belong  to 
the  two  genera  Belostoma  and  Banacus,  distinguished  from  each 
other  by  the  fact  that  Belostoma  has  a  groove  on  the  under  side  of 
the  femur  of  the  front  leg,  for  the  reception  of  the  tibia. 

The  salivary  glands  of  Belostoma  were  figured  by  Leidy  (1847) 
and  later  were  studied  in  more  detail  by  Locy  (1884).  There  are 
two  pairs  of  the  glands,  those  of  one  pair  being  long  and  extending 
back  as  far  as  the  beginning  of  the  abdomen,  while  the  others  are 
about  one-fourth  as  long.  They  lie  on  either  side  of  the  oesophagus. 
On  each  side  of  the  oesophagus  there  is  a  slender  tube  with  a 
sigmoid  swelling  which  may  serve  as  a  poison  reservoir.  In  addi- 
tion to  this  salivary  system,  there  is  a  pair  of  very  prominent  glands 
on  the  ventral  side  of  the  head,  opening  just  above  the.,base  of  the 
beak.  These  Locy  has  called  the  "cephalic  glands"  and  he  suggests 
that  they  are  the  source  of  the  poison.  They  are  the  homologues 
of  the  maxillary  glands  described  for  other  Hemiptera,  and  it  is  by 
no  means  clear  that  they  are  concerned  with  the  production  of 
venom.  It  seems  more  probable  that  in  Belostoma,  as  in  other 
Hemiptera,  it  is  produced  by  the  salivary  glands,  though  the  question 
is  an  open  one. 

The  Belostomatidae  feed  not  only  on  insects,  but  on  small  frogs, 
fish,  salamanders  and  the  like.  Matheson  (1907)  has  recorded  the 
killing  of  a  good-sized  bird  by  Belostoma  americana.     A  woodpecker, 


Hemiptera,  or  True  Bugs 


31 


or  flicker,  was  heard  to  utter  cries  of  distress, 
and  fluttered  and  fell  from  a  tree.  On  exam- 
ination it  was  found  that  a  bug  of  this  species 
had  inserted  its  beak  into  the  back  part  of 
the  skull  and  was  apparently  busily  engaged 
in  sucking  the  blood  or  brains  of  the  bird. 
Various  species  of  Belostoma  have  been  cited 
as  causing  painful  bites  in  man.  We  can 
testify  from  personal  experience  that  the  bite 
of  Belostoma  americana  may  almost  immedi- 
ately cause  severe, 
shooting     pains    that 


20.     Reduvius  COpsicoetus) 

personatus.  (x2). 


may  extend  through- 
out the  arm  and   that 
they  may  be  felt  for  several  days. 

Relief  from  the  pain  may  be  obtained  by 
the  use  of  dilute  ammonia,  or  a  menthol 
ointment.  In  the  not  uncommon  case  of 
secondary  infection  the  usual  treatment  for 
that  should  be  adopted. 

The  ReduviidaB,  or  assassin-hugs  are  cap- 
able   of    inflicting    very    painful  wounds,   as 

most  collect- 
ors of  Hemip- 
tera know  to 
their 


'» 

1- 

'^m 

..^^' 

'»i 

4 

^-4 

%^: 

n 

f  ^ 

W 

•;'\ 

5| 

* 

•<w 

21. 


(o)  Reduviu.'i  personatus, 
nymph. 
Photograph  by  M.  V.  S. 

sorrow. 
Some  species  are  frequently  to  be 
found  in  houses  and  outhouses  and 
Dr.  Howard  suggests  that  many  of 
the  stories  of  painful  spider  bites 
relate  to  the  attack  of  these  forms. 

An  interesting  psychological  study 
was  afforded  in  the  siunmer  of  1899, 
by  the  "kissing-bug"  scare  which 
swept  over  the  country.  It  was 
reported  in  the  daily  papers  that  a 
new  and  deadly  bug  had  made  its 
appearance,  which  had  the  impleasant 
'^h^tiTZllTuTs"'"'"''^""^     habit  of  choosing  the  lips  or  cheeks 


32 


Poisonous  Arthropods 


22.     Rasahus  biguttatus.  (x2).     After    j^gi-j^-^ 
Howard 


for  its  point  of  attack  on  man.     So  widespread  were  the   stories 
regarding  this  supposedly  new  insect  that  station  entomologists  all 

over  the  country  began  to  receive  sus- 
pected specimens  for  identification.  At 
Cornell  there  were  received,  among 
others,  specimens  of  stone-flies,  may- 
flies and  even  small  moths,  with  in- 
quiries as  to  whether  they  were  "kiss- 
ing-bugs." 

Dr.  L.  0.  Howard  has  shown  that  the 
scare  had  its  origin  in  newspaper  reports 
of  some  instances  of  bites  by  either 
Melanolestes  picipes  (fig.  19a)  or  Opsi- 
coetes  personatus  (fig.  20),  in  the  vicinity 
of  Washington,  D.  C.  He  then  discusses 
in  considerable  detail  the  more  promi- 
of  the  Reduviidse  which,  with 
greater  or  less  frequency  pierce  the  skin 
of  human  beings.  These  are  Opsicoetes  personatus,  Melanolestes 
picipes,  Coriscus  subcoleoptratus  (fig.  igg),  Rasahus  thoracicus. 
Rasahus  biguttatus  (fig.  22),  Conorhinus  sanguisugus  (fig.  71),  and  C. 
ahdominalis  (fig.  23). 

One  of  the  most  interesting  of  these  species  is  Reduvius  personatus, 
{  =  OpsiccBtus  personatus),  which  is  popularly  known  as  the  "masked 
bed-bug  hunter."  It  owes  this 
name  to  the  fact  that  the  imma- 
ture nymphs  (fig.  21)  have  their 
bodies  and  legs  completely  covered 
by  dust  and  lint,  and  that  they 
are  supposed  to  prey  upon  bed- 
bugs. LeConte  is  quoted  by  How- 
ard as  stating  that  "This  species  is 
remarkable  for  the  intense  pain 
caused  by  its  bite.  I  do  not  know 
whether  it  ever  willingly  plunges 
its  rostrum  into  any  person,  but 
when  caught,  or  unskilfully  handled 
it  always  stings.  In  this  case  the 
pain  is  almost  equal  to  the  bite  of  a  snake,  and  the  swelHng  and 
irritation  which  result  from  it  will  sometimes  last  for  a  week." 


Conorhinus  abdominalis  (.\2). 
Marlatt. 


After 


Dipt  era  33 

A  species  which  very  commonly  attacks  man  is  Conorhinus 
sanguisugns,  the  so-called  "big  bed-bug"  of  the  south  and  southern 
United  States.  It  is  frequently  found  in  houses  and  is  known  to 
inflict  an  exceedingly  painful  bite.  As  in  the  case  of  a  number  of 
other  predaceous  Hemiptera,  the  salivary  glands  of  these  forms  are 
highly  developed.  The  efifect  of  the  bite  on  their  prey  and,  as  Marlatt 
has  pointed  out,  the  constant  and  uniform  character  of  the  symptoms 
in  nearly  all  cases  of  bites  in  man,  clearly  indicate  that  their  saliva 
contains  a  specific  substance.  No  satisfactory  studies  of  the  secre- 
tions have  been  made.  On  the  other  hand,  Dr.  Howard  is  doubt- 
less right  in  maintaining  that  the  very  serious  results  which  some- 
times follow  the  bite  are  due  to  the  introduction  of  extraneous  poison 
germs.  This  is  borne  out  by  the  symptoms  of  most  of  the  cases 
cited  in  literature  and  also  by  the  fact  that  treatment  with  corrosive 
sublimate,  locally  applied  to  the  woiind,  has  yielded  favorable  results. 

Other  Hemiptera  Reported  as  Poisonous  to  Man — ^A  large  number 
of  other  Hemiptera  have  been  reported  as  attacking  man.  Of  these, 
there  are  several  species  of  Lygseidce,  Coreidae,  and  Capsidae.  Of  the 
latter,  Lygus  pratensis,  the  tarnished  plant-bug,  is  reported  by 
Professor  Crosby  as  sucking  blood.  Orthotylus  flawsparsus  is  another 
Capsid  which  has  been  implicated.  Empoasca  mali  SinaPlatymetopms 
acutus  of  the  Jassidas  have  also  been  reported  as  having  similar 
habits. 

Whenever  the  periodical  cicada  or  "seventeen-year  locust"  be- 
comes abundant,  the  newspapers  contain  accounts  of  serious  results 
from  its  bites.  The  senior  author  has  made  scores  of  attempts  to 
induce  this  species  to  bite  and  only  once  successfully.  At  that 
time  the  bite  was  in  no  wise  more  severe  than  a  pin-prick.  A  stu- 
dent in  our  department  reports  a  similar  experience.  There  is  no 
case  on  record  which  bears  evidence  of  being  worthy  of  any  credence, 
whatsoever. 

Under  the  heading  of  poisonous  Hemiptera  we  might  consider  the 
bed-bugs  and  the  lice.  These  will  be  discussed  later,  as  parasites 
and  as  carriers  of  disease,  and  therefore  need  only  be  mentioned  here. 

DIPTERA 

Several  species  of  blood-sucking  Diptera  undoubtedly  secrete  a 
saliva  possessing  poisonous  properties.  Chief  among  these  are  the 
Culicidse,  or  mosquitoes,  and  the  Simuliidse,  or  black-flies.  As  we 
shall  consider  these  forms  in  detail  under  the  heading  of  parasitic 


34  Poisonous  Arthropods 

species  and  insects  transmitting  disease,  we  shall  discuss  here  only 
the  poison  of  the  mosquitoes. 

It  is  well  known  that  mosquitoes,  when  they  bite,  inject  into  the 
woimd  a  minute  quantity  of  poison.  The  effect  of  this  varies  accord- 
ing to  the  species  of  mosquito  and  also  depends  verv^  much  on  the 
susceptibility  of  the  individual.  Soon  after  the  bite  a  sensation  of 
itching  is  noticed  and  often  a  wheal,  or  eminence,  is  produced  on  the 
skin,  which  may  increase  to  a  considerable  swelling.  The  scratching 
which  is  induced  may  cause  a  secondare'  infection  and  thus  lead  to 
serious  restdts.  Some  people  seem  to  acquire  an  immunity  against 
the  poison. 

The  ptirpose  of  this  irritating  fluid  may  be,  as  Reaiunur  suggested, 
to  prevent  the  coagiilation  of  the  blood  and  thus  not  only  to  cause 
it  to  flow  freely  when  the  insect  bites  but  to  prevent  its  rapid  coagula- 
tion in  the  stomach.  Ob\'iously,  it  is  not  developed  as  a  protective 
fluid,  and  its  presence  subjects  the  group  to  the  additional  handicap 
of  the  vengeance  of  man. 

As  to  the  origin  of  the  poison,  there  has  been  httle  question, 
until  recent  years,  that  it  was  a  secretion  from  the  salivary  glands. 

Macloskie  (1888)  showed 
that  each  gland  is  sub- 
divided into  three  lobes, 
the  middle  of  which  differs 
from  the  others  in  having 

'"G^^AaJtc  nerve  ^ng^Mx  ^ — tectum 

evenh^  granulated  contents 

24.     Diagram  of  a  longitudinal  section  of  a  mosquito.  ,     '       .     .  ,  - 

and  stammg  more  deeply 
than  the  others  (fig.  24).  This  middle  lobe  he  regarded  as  the  source 
of  the  poison.  Bruck,  (191 1),  by  the  use  of  water,  glycerine,  chloro- 
form, and  other  fluids,  extracted  from  the  bodies  of  a  large  niunber 
of  mosquitoes  a  toxine  which  he  calls  culicin.  This  he  assumes 
comes  from  the  salivary  glands.  Animal  experimentation  showed 
that  this  extract  possessed  hemolytic  powers.  Inoculated  into  the 
experimenter's  own  skin  it  produced  lesions  which  behaved  exactly 
as  do  those  of  mosquito  bites. 

Similarly,  most  writers  on  the  subject  have  concurred  with  the 
view  that  the  salivar\^  glands  are  the  source  of  the  poison.  How- 
ever, recent  work,  especially  that  of  Nuttall  and  Shipley  (1903), 
and  Schaudinn  (1904),  has  shown  that  the  evidence  is  by  no  means 
conclusive.  Nuttall  dissected  out  six  sets  (thirty-six  acini)  of  glands 
from  freshly  killed  Culex  pipiens  and  placed  them  in  a  drop  of  salt 


Diptera  3  5 

solution.  The  drop  was  allowed  to  dn-,  it  being  thought  that  the 
salt  cn^stals  would  facilitate  the  grinding  up  of  the  glands  with  the 
end  of  a  small  glass  rod,  this  being  done  under  microscopic  control. 
After  grinding  up,  a  small  drop  of  water  was  added  of  the  size  of  the 
original  drop  of  saline,  and  an  equal  volume  of  human  blood  taken 
from  the  clean  finger-tip  was  quickly  mixed  therewith,  and  the  whole 
dra^^^l  up  into  a  capillar}^  tube.  Clotting  was  not  prevented  and  no 
hemoh'sis  occurred.  Salivary  gland  emulsion  added  to  a  dilute 
suspension  of  corpuscles  did  not  lead  to  hemolysis.  This  experi- 
ment was  repeated  a  number  of  times,  with  slight  modification,  but 
with  similar  results.  The  data  obtained  from  the  series  "do  not 
support  the  hypothesis  that  the  salivary  glands,  at  any  rate  in  Culex 
pipiens,  contain  a  substance  which  prevents  coagulation." 

Much  more  detailed,  and  the  more  important  experiments  made 
along  this  line,  are  those  of  Schaudinn  (1904).  The  results  of  these 
experiments  were  published  in  connection  with  a  technical  paper 
on  the  alternation  of  generations  and  of  hosts  in  Trypanosoma  and 
SpirochcEta,  and  for  this  reason  seem  to  have  largely  escaped  the  notice 
of  entomologists.  They  are  so  suggestive  that  we  shall  refer  to  them 
in  some  detail. 

Schaudinn  obser^^ed  that  the  three  oesophageal  diverticula  (com- 
monly, but  incorrectly,  known  as  the  "sucking  stomach")  (fig.  24) 
usually  contain  large  bubbles  of  gas  and  in  addition,  he  alwa^^s  found 
yeast  cells.  On  the  groiind  of  numerous  obser\^ations,  Schaudinn 
was  convinced  that  these  yeast  plants  are  normal  and  constant 
commensals  of  the  insect.  He  regarded  them  as  the  cause  of  the  gas 
bubbles  to  be  found  in  diverticiila.  It  was  found  that  as  the  insect 
fed,  from  time  to  time  the  abdomen  unden\^ent  convulsive  contrac- 
tions which  resulted  in  the  emptying  of  the  oesophageal  diverticula  and 
the  salivan,^  glands  through  blood  pressure. 

In  order  to  test  the  supposed  toxic  action  of  the  salivan'-  glands, 
Schaudinn  repeatedly  introduced  them  under  his  skin  and  that  of 
his  assistant,  in  a  drop  of  salt  solution,  and  never  obtained  a  sugges- 
tion of  the  irritation  following  a  bite  of  the  insect,  even  though  the 
glands  were  carefully  rubbed  to  fragments  after  their  implantation. 
Like  NuttaU,  he  failed  to  get  satisfactory^  evidence  that  the  secre- 
tion of  the  salivar}^  glands  retarded  coagulation  of  the  blood. 

He  then  carefully  removed  the  oesophageal  diverticula  with  their 
content  of  yeast  and  introduced  them  into  an  opening  in  the  skin 
of  the  hand.     Within  a  few  seconds  there  was  noticeable  the  charac- 


36  Poisonous  Arthropods 

teristic  itching  irritation  of  the  mosquito  bite;  and  in  a  short  time 
there  appeared  reddening  and  typical  swelling.  This  was  usually 
much  more  severe  than  after  the  usual  mosquito  bite,  and  the  swell- 
ing persisted  and  itched  longer.  This  was  because  by  the  ordinary 
bite  of  the  mosquito  most  of  the  yeast  cells  are  again  sucked  up, 
while  in  these  experiments  they  remained  in  the  wound.  These 
experiments  were  repeated  a  number  of  times  on  himself,  his  assistant 
and  others,  and  always  with  the  same  result.  From  them  Schaudinn 
decided  that  the  poisonous  action  of  the  mosquito  bite  is  caused  by 
an  enzyme  from  a  commensal  fungus.  These  conclusions  have  not, 
as  yet,  been  satisfactorily  tested. 

Relief  from  the  effect  of  the  mosquito  bite  may  be  obtained  by 
bathing  the  swellings  with  weak  ammonia  or,  according  to  Howard, 
by  using  moist  soap.  The  latter  is  to  be  rubbed  gently  on  the  punc- 
ture and  is  said  to  speedily  allay  the  irritation.  Howard  also  quotes 
from  the  Journal  of  Tropical  Medicine  and  Hygiene  to  the  effect  that 
a  few  drops  of  a  solution  of  thirty  to  forty  grains  of  iodine  to  an  ounce 
of  saponated  petroleum  rubbed  into  the  mosquito  bite,  or  wasp  sting, 
allay  the  pain  instantaneously. 

Methods  of  mosquito  control  will  be  discussed  later,  in  consider- 
ing these  insects  as  parasites  and  as  carriers  of  disease. 

STINGING  INSECTS 

The  stinging  insects  all  belong  to  the  order  Hymenoptera.  In  a 
number  of  families  of  this  group  the  ovipositor  is  modified  to  form  a 
sting  and  is  connected  with  poison-secreting  glands.  We  shall 
consider  the  apparatus  of  the  honey-bee  and  then  make  briefer  refer- 
ence to  that  of  other  forms. 

Apis  mellifica,  the  honey  bee — The  sting  of  the  worker  honey- 
bee is  situated  within  a  so-called  sting  chamber  at  the  end  of  the 
abdomen.  This  chamber  is  produced  by  the  infolding  of  the  greatly 
reduced  and  modified  eighth,  ninth  and  tenth  abdominal  segments 
into  the  seventh.*  From  it  the  dart-like  sting  can  be  quickly  ex- 
serted. 

The  sting  (fig.  25)  is  made  up  of  a  central  shaft,  ventro-laterad  of 
which  are  the  paired  lancets,  or  darts,  which  are  provided  with  sharp, 
recurved  teeth.     Still  further  laterad  lie  the  paired  whitish,  finger- 


*It  should  be  remembered  that  in  all  the  higher  Hyrnenoptera  the  first  ab- 
dominal segment  is  fused  with  the  thorax  and  that  what  is  apparently  the  sixth 
segment  is,  in  reality,  the  seventh. 


Stinging  Insects 


37 


Sting  of  a  honey  bee.  Psn  Sc,  base  of  acid 
poison  gland;  B  Gl.  alkaline  poison  gland; 
Stn  Pip,  sting  palpi;  Sk  B,  bulb  of  sting; 
Sh  A,  basal  arm;  Let,  lancets  or  darts;  Sh  s, 
shaft  of  sting.     Modified  from  Snodgrass. 


like  sting  palpi.  Comparative  mori^hological  as  well  as  embryologi- 
cal  studies  have  clearly  established  that  these  three  parts  corres- 
pond to  the  three  pairs  of 
gonopophyses  of  the  o\dpositor 
of  more  generalized  insects. 

An  examination  of  the  inter- 
nal structures  (fig.  26)  reveals 
two  distinct  types  of  poison 
glands,  the  acid-secreting  and 
the  alkaline-secreting  glands, 
and  a  prominent  poison  reser- 
voir. In  addition,  there  is  a 
small  pair  of  accessory  struct- 
ures which  have  been  called  lubricating  glands,  on  account  of  the 
supposed  function  of  their  product.  The  acid-secreting  gland  empties 
into  the  distal  end  of  the  poison  reserv^oir  which  in  turn  pours  the 
secretion  into  the  muscular  bulb-like  enlargement  at  the  base  of  the 
shaft.  The  alkaline  secreting  gland  empties  into  the  bulb  ventrad 
of  the  narrow  neck  of  the  resen^oir. 

The  poison  is  usually  referred  to  as  formic  acid.  That  it  is  not  so 
easily  explained  has  been  repeatedly  shown  and  is  evidenced  by  the 
presence  of  the  two  types  of  glands.  Carlet  maintains  that  the  pro- 
duct of  either  gland  is  in  itself  innocent, 
— it  is  only  when  they  are  combined  that 
the  toxic  properties  appear. 

The  most  detailed  study  of  the  poison 
of  the  honey-bee  is  that  of  Josef  Langer 
(1897),  who  in  the  course  of  his  work  used 
some  25,000  bees.  Various  methods  of 
obtaining  the  active  poison  for  experi- 
mental purposes  were  used.  For  obtaining 
the  pure  secretion,  bees  were  held  in  the 
fingers  and  compressed  imtil  the  sting  was 
exserted,  when  a  clear  drop  of  the  poison 
was  visible  at  its  tip.  This  was  then  taken 
up  in  a  capillary  tube  or  dilute  solutions 
obtained  by  dipping  the  tip  of  the  sting  into 
a  definite  amotmt  of  distilled  water. 
An  aqueous  solution  of  the  poison  was  more  readily  obtained  by 
pulling  out  the  sting  and  poison  sacs  by  means  of  forceps,  and  grinding 


Poison  apparatus  of  a  honey 
bee.  Modified  from  Snod- 
grass. 


38  Poisonous  Arthropods 

them  up  in  water.  The  somewhat  clouded  fluid  was  then  filtered 
one  or  more  times.  For  obtaining  still  greater  quantities,  advantage 
was  taken  of  the  fact  that  while  alcohol  coagulates  the  poison,  the 
active  principle  remains  soluble  in  water.  Hence  the  stings  with 
the  annexed  glands  where  collected  in  96  per  cent  alcohol,  after 
filtering  off  of  the  alcohol  were  dried  at  40°  C,  then  rubbed  to  a  fine 
powder  and  this  was  repeatedly  extracted  with  water.  Through 
filtering  of  this  aqueous  extract  there  was  obtained  a  yellowish- 
brown  fluid  which  produced  the  typical  reactions,  according  to  con- 
centration of  the  poison. 

The  freshly  expelled  drop  of  poison  is  limpid,  of  distinct  acid 
reaction,  tastes  bitter  and  has  a  delicate  aromatic  odor.  On  evapora- 
tion, it  leaves  a  sticky  residue,  which  at  100  degrees  becomes  fissured, 
and  suggests  dried  gum  arabic.  The  poison  is  readily  soluble  in 
water  and  possesses  a  specific  gravity  of  1.1313.  On  drying  at  room 
temperature,  it  leaves  a  residue  of  30  per  cent,  which  has  not  lost  in 
poisonous  action  or  in  solubility.  In  spite  of  extended  experiments, 
Langer  was  unable  to  determine  the  nature  of  the  active  principle. 
He  showed  that  it  was  not,  as  had  been  supposed,  an  albuminous 
body,  but  rather  an  organic  base. 

The  pure  poison,  or  the  two  per  cent  aqueous  solution,  placed  on 
the  uninjured  skin  showed  absolutely  no  irritating  effect,  though  it 
produced  a  marked  reaction  on  the  mucus  membrane  of  the  nose  or 
eye.  A  single  drop  of  one-tenth  per  cent  aqueous  solution  of  the 
poison  brought  about  a  typical  irritation  in  the  conjunctiva  of  the 
rabbit's  eye.  On  the  other  hand,  the  application  of  a  drop  of  the 
poison,  or  its  solution,  to  the  slightest  break  in  the  skin,  or  by  means 
of  a  needle  piercing  the  skin,  produced  typical  effects.  There  is  pro- 
duced a  local  necrosis,  in  the  neighborhood  of  which  there  is  infiltra- 
tion of  lymphocytes,  oedema,  and  hypersemia. 

The  effect  of  the  sting  on  man  (fig.  27)  is  usually  transitory  but 
there  are  some  individuals  who  are  made  sick  for  hours,  by  a  single 
sting.  Much  depends,  too,  on  the  place  struck.  It  is  a  common 
experience  that  an  angry  bee  will  attempt  to  reach  the  eye  of  its 
victim  and  a  sting  on  the  lid  may  resiilt  in  severe  and  prolonged 
swelling.  In  the  case  of  a  man  stung  on  the  cheek,  Legiehn  observed 
complete  aphonia  and  a  breaking  out  of  red  blotches  all  over  the 
body.  A  sting  on  the  tongue  has  been  known  to  cause  such  collateral 
oedema  as  to  endanger  life  through  suffocation.  Cases  of  death  of 
man  from  the  attacks  of  bees  are  rare  but  are  not  unknown.     Such 


Stinging  Insects  39 

results  are  usually  from  a  number  of  stings  but,  rarely,  death  has 
been  known  to  follow  a  single  sting,  entering  a  blood  vessel  of  a 
particularly  susceptible  individual. 

It  is  clearly  established  that  partial  immunity  from  the  effects 
of  the  poison  may  be  acquired.  By  repeated  injections  of  the  venom, 
mice  have  been  rendered  capable  of  bearing  doses  that  certainly 
would  have  killed  them  at  first.  It  is  a  well-known  fact  that  most 
bee-keepers  become  gradually  hardened  to  the  stings,  so  that  the 
irritation  and  the  swelling  become  less  and  less.     Some  individuals 


J- 

Efifect  of  bee  stings.     After  Root. 

have  found  this  immunity  a  temporary  one,  to  be  reacquired  each 
season.  A  striking  case  of  acquired  immunity  is  related  by  the 
Roots  in  their  "A  B  C  and  X  Y  Z  of  Bee  Culture."  The  evidence 
in  the  case  is  so  clear  that  it  should  be  made  more  widely  available 
and  hence  we  quote  it  here. 

A  young  man  who  was  determined  to  become  a  bee-jkeeper,  was  so 
susceptible  to  the  poison  that  he  was  most  seriously  affected  by  a 
single  sting,  his  body  breaking  out  with  red  blotches,  breathing  grow- 
ing difficult,  and  his  heart  action  being  painfully  accelerated.  "We 
finally  suggested  taking  a  live  bee  and  pressing  it  on  the  back  of  his 
hand  until  it  merely  pierced  his  skin  with  the  sting,  then  immediately 
brushing  off  both  bee  and  sting.  This  was  done  and  since  no  serious 
effect  followed,  it  was  repeated  inside  of  four  or  five  days.  This 
was  continued  for  some  three  or  four  weeks,  when  the  patient  began  to 
have  a  sort  of  itching  sensation  all  over  his  bod}-.     The  hypodermic 


40  Poisonous  Arthropods 

injections  of  bee-sting  poison  were  then  discontinued.  At  the  end 
of  a  month  they  were  repeated  at  intervals  of  four  or  five  days. 
Again,  after  two  or  three  weeks  the  itching  sensation  came  on,  but 
it  was  less  pronounced.  The  patient  was  given  a  rest  of  about  a 
month,  when  the  doses  were  repeated  as  before."  By  this  course 
of  treatment  the  young  man  became  so  thoroughly  immunized  that 
neither  unpleasant  results  nor  swelling  followed  the  attacks  of  the 
insects  and  he  is  able  to  handle  bees  with  the  same  freedom  that  any 
experienced  bee-keeper  does. 

In  an  interesting  article  in  the  Entomological  News  for  November, 
1 9 14,  J.  H.  Lovell  calls  attention  to  the  fact  that  "There  has  been  a 
widespread  belief  among  apiarists  that  a  beekeeper  will  receive  more 
stings  when  dressed  in  black  than  when  wearing  white  clothing. 
A  large  amount  of  evidence  has  been  published  in  the  various  bee 
journals  showing  beyond  question  that  honey-bees  under  certain 
conditions  discriminate  against  black.  A  few  instances  may  be 
cited  in  illustration.  Of  a  flock  of  twelve  chickens  running  in  a  bee- 
yard  seven  black  ones  were  stung  to  death,  while  five  light  colored 
ones  escaped  uninjured.  A  white  dog  ran  among  the  bee-hives 
without  attracting  much  attention,  while  at  the  same  time  a  black 
dog  was  furiously  assailed  by  the  bees.  Mr.  J.  D.  Byer,  a  prominent 
Canadian  beekeeper,  relates  that  a  black  and  white  cow,  tethered 
about  forty  feet  from  an  apiary,  was  one  afternoon  attacked  and 
badly  stung  by  bees.  On  examination  it  was  found  that  the  black 
spots  had  five  or  six  stings  to  one  on  the  white.  All  noticed  this  fact, 
although  no  one  was  able  to  offer  any  explanation.  A  white  horse 
is  in  much  less  danger  of  being  stung,  when  driven  near  an  apiary, 
than  a  black  one.  It  has,  indeed,  been  observed  repeatedly  that 
domestic  animals  of  all  kinds,  if  wholly  or  partially  black,  are  much 
more  hable  to  be  attacked  by  bees,  if  they  wander  among  the  hives, 
than  those  which  are  entirely  white. 

In  order  to  test  the  matter  experimentally,  the  following  series 
of  experiments  was  performed.  In  the  language  of  the  investi- 
gator : 

"On  a  clear,  warm  day  in  August  I  dressed  wholly  in  white  with 
the  exception  of  a  black  veil.  Midway  on  the  sleeve  of  my  right  arm 
there  was  sewed  a  band  of  black  cloth  ten  inches  wide.  I  then 
entered  the  bee-yard  and,  removing  the  cover  from  one  of  the  hives, 
lifted  a  piece  of  comb  with  both  hands  and  gently  shook  it.  Instantly 
many  of  the  bees  flew  to  the  black  band,  which  they  continued  to 


Stinging  Insects  41 

attack  as  long  as  they  were  disturbed.  Not  a  single  bee  attempted 
to  sting  the  left  sleeve,  which  was  of  course  entirely  white,  and  very 
few  even  alighted  upon  it." 

"This  experiment  was  repeated  a  second,  third  and  fourth  time; 
in  each  instance  ^vith  similar  results.  I  estimated  the  number  of  bees 
on  the  band  of  black  cloth  at  various  moments  was  from  thirty  to 
forty;  it  was  evident  from  their  behavior  that  they  were  extremely 
irritable.  To  the  left  white  sleeve  and  other  portions  of  my  clothing 
they  paid  very  little  attention ;  but  the  black  veil  was  very  frequently 
attacked." 

"A  few  days  later  the  experiments  were  repeated,  but  the  band  of 
black  cloth,  ten  inches  wide,  was  sewed  around  my  left  arm  instead 
of  around  the  right  arm  as  before.  When  the  bees  were  disturbed, 
after  the  hive  cover  had  been  removed,  they  fiercely  attacked  the 
band  of  black  cloth  as  in  the  previous  experiences ;  but  the  right  white 
sleeve  and  the  white  suit  were  scarcely  noticed.  At  one  time  a  part 
of  the  black  cloth  was  almost  literally  covered  with  furiously  stinging 
bees,  and  the  black  veil  was  assailed  by  hundreds.  The  bees  behaved 
in  a  similar  manner  when  a  second  hive  on  the  opposite  side  of  the 
apiary  w^as  opened." 

'  'A  white  veil  which  had  been  procured  for  this  purpose,  was  next 
substituted  for  the  black  veil.  The  result  was  most  surprising, 
for,  whereas  in  the  previous  experiments  hundreds  of  bees  had 
attacked  the  black  veil,  so  few  flew  against  the  white  veil  as  to  cause 
me  no  inconvenience.  Undoubtedly  beekeepers  \vill  find  it  greatly 
to  their  advantage  to  wear  white  clothing  when  working  among  their 
colonies  of  bees  and  manipulating  the  frames  of  the  hives." 

When  a  honey-bee  stings,  the  tip  of  the  abdomen,  with  the  entire 
sting  apparatus,  is  torn  off  and  remains  in  the  wound.  Here  the 
muscles  continue  to  contract,  for  some  minutes,  forcing  the  barbs 
deeper  and  deeper  into  the  skin,  and  forcing  out  additional  poison 
from  the  reservoir. 

Treatment,  therefore,  first  consists  in  removing  the  sting  without 
squeezing  out  additional  poison.  This  is  accomplished  by  lifting 
and  scraping  it  out  with  a  knife-blade  or  the  fingernail  instead  of 
grasping  and  pulling  it  out.  Local  application  of  alkalines,  such  as 
weak  ammonia,  are  often  recommended  on  the  assumption  that  the 
poison  is  an  acid  to  be  neutralized  on  this  manner,  but  these  are  of 
little  or  no  avail.  They  should  certainly  not  be  rubbed  in,  as  that 
woiild  only  accelerate  the  absorption  of  the  poison.      The  use  of 


42  Poisonous  Arthropods 

cloths  wrung  out  in  hot  water  and  applied  as  hot  as  can  be  borne, 
affords  much  relief  in  the  case  of  severe  stings.  The  application  of 
wet  clay,  or  of  the  end  of  a  freshly  cut  potato  is  sometimes  helpful. 
In  extreme  cases,  where  there  is  great  susceptibility,  or  where 
there  may  have  been  many  stings,  a  physician  should  be  called.  He 
may  find  strychnine  injections  or  other  treatment  necessary,  if 
general  symptoms  develop. 

Other  Stinging  Forms — Of  the  five  thousand,  or  more,  species 
of  bees,  most  possess  a  sting  and  poison  apparatus  and  some  of  the 
larger  forms  are  capable  of  inflicting  a  much  more  painful  sting  than 


28.     The  poison  apparatus  of  Formica.     Wheeler,  after  Forel. 

that  of  the  common  honey-bee.  In  fact,  some,  like  the  bumble  bees, 
possess  the  advantage  that  they  do  not  lose  the  sting  from  once  using 
it,  but  are  capable  of  driving  it  in  repeatedly.  In  the  tropics  there 
are  found  many  species  of  stingless  bees  but  these  are  noted  for  their 
united  efforts  to  drive  away  intruders  by  biting.  Certain  species 
possess  a  ver}^  irritating  saliva  which  they  inject  into  the  wounds. 

The  ants  are  not  ordinarily  regarded  as  worthy  of  consideration 
under  the  heading  of  "stinging  insects"  but  as  a  matter  of  fact, 
most  of  them  possess  well  developed  stings  and  some  of  them,  especi- 
ally in  the  tropics,  are  very  justly  feared.  Even  those  which  lack 
the  sting  possess  well-developed  poison  glands  and  the  parts  of  the 
entire  stinging  apparatus,  in  so  far  as  it  is  developed  in  the  various 
species,  may  readily  be  homologized  with  those  of  the  honey-bee. 


Stinging  Insects 


43 


The  ants  lacking  a  sting  are  those  of  the  subfamily  Camponotinae, 
which  includes  the  largest  of  our  local  species.  It  is  an  interesting 
fact  that  some  of  these  species  possess  the  largest  poison  glands  and 
reservoir  (fig.  28)  and  it  is  found  that  when  they  attack  an  enemy 
they  bring  the  tip  of  the  abdomen  forward  and  spray  the  poison  in 
such  a  way  that  it  is  introduced  into  the  wound  made  by  the  powerful 
mandibles. 

More  feared  than  any  of  the  other  Hymenoptera  are  the  hornets 
and  wasps.     Of  these  there  are  many  species,  some  of  which  attain 


29.     A  harmless,  but  much  feared  larva,  the  "tomato  worm." 
Natural  size.     Photograph  by  M.  V.  S. 

a  large  size  and  are  truly  formidable.  Phisalix  (1897),  has  made  a 
study  of  the  venom  of  the  common  hornet  and  finds  that,  like  the 
poison  of  the  honey-bee,  it  is  neither  an  albiiminoid  nor  an  alkaloid. 
Its  toxic  properties  are  destroyed  at  120''  C.  Phisalix  also  says  that 
the  venom  is  soluble  in  alcohol.  If  this  be  true,  it  differs  in  this 
respect  from  that  of  the  bee.  An  interesting  phase  of  the  work  of 
Phisalix  is  that  several  of  her  experiments  go  to  show  that  the  venom 
of  hornets  acts  as  a  vaccine  against  that  of  vipers. 


NETTLING  INSECTS 

So  far,  we  have  considered  insects  which  possess  poison  glands 
connected  with  the  mouth-parts  or  a  special  sting  and  which  actively 


44 


Poisonous  Arthropods 


inject  their  poison  into  man.  There  remain  to  be  considered  those 
insects  which  possess  poisonous  hairs  or  body  fluids  which,  under 
favorable  circumstances,  may  act  as  poisons.  To  the  first  of  these 
belong  primarily  the  larvae  of  certain  Lepidoptera. 


LEPIDOPTERA 


When  we  consider  the  reputedly  poisonous  larvae  of  moths  and 
butterflies,  one  of  the  first  things  to  impress  us  is  that  we  cannot 


30.     Another  innocent  but  much  maligned  caterpillar,  the  larva  of  the  Regal  moth. 
Photograph  by  M.  V.  S. 

judge  by  mere  appearance.  Various  species  of  Sphingid,  or  hawk- 
moth  larvae,  bear  at  the  end  of  the  body  a  chitinous  horn,  which  is 
often  referred  to  as  a  "sting"  and  regarded  as  capable  of  inflicting 
dangerous  wounds.  It  would  seem  unnecessary  to  refer  to  this 
absurd  belief  if  it  were  not  that  each  summer  the  newspapers  con- 
tain supposed  accounts  of  injury  from  the  "tomato  worm"  (fig.  29) 
and  others  of  this  group.  The  grotesque,  spiny  larva  (fig.  30)  of 
one  of  our  largest  moths,  Cither  onia  re  gaits  is  much  feared  though 
perfectly  harmless,  and  similar  instances  could  be  multipHed. 

But  if  the  larvae  are  often  misjudged  on  account  of  their  ferocious 
appearance,  the  reverse  may  be  true.  A  group  of  most  innocent 
looking  and  attractive  caterpillars  is  that  of  the  flannel-moth  larvae, 


Nettling  Insects 


45 


of  which  Lagoa  crispata  may  be  taken  as  an  example.     Its   larva 
(fig.  31)  has  a  very  short  and  thick  body,  which  is  fleshy  and  com- 


31.     The  flmnel  moth  (Lagoa  crispata).     (a)  Poisonous  larva. 


31.     '6)  Adult.     Enlarged.     Photographs  by  M.  V.  S. 

pletely  covered  and  hidden  by  long  silken  hairs  of  a  tawny  or  brown 
color,  giving  a  convex  form  to  the  upper  side.     Interspersed  among 


46 


Poisonous  Arthropods 


32    The  poisonous  saddle  back  caterpillar, 

(Sibine)  stimulea.     Photograph  by  M.  V.  S. 


Empretia 


these  long  hairs  are  numer- 
ous short  spines  connected 
with  underlying  h\Tpoder- 
mal  poison  glands.  These 
hairs  are  capable  of  pro- 
ducing a  marked  nettling 
effect  when  they  come  in 
contact  with  the  skin. 
This  species  is  found  in 
our  Atlantic  and  Southern 
States.  Satisfactory 
studies  of  its  poisonous 
hairs  and  their  glands  have 
not  yet  been  made. 

Sibine  stimulea  {Em- 
pretia stimulea),  or  the 
saddle-back  caterpillar 

(fig.  32),  is  another  which  possesses    nettling   hairs.      This  species 

belongs  to  the  group  of  Eucleidae,  or  slug  caterpillars.     It  can  be 

readily  recognized 

by     its    flattened 

form ,  lateral ,  brist- 
ling spines  and  by 

the     large     green 

patch  on  the  back 

resembling    a 

saddle-cloth,  while 

the  saddle  is  repre- 
sented by  an  oval, 

purplish-brown 

spot.      The  small 

spines    are   veno- 
mous   and    affect 

some  persons  very 

painfully.      The 

larva  feeds  on  the 

leaves  of  a  large 

variety   of    forest 

trees  and  also  on 

cherr3%  plum,  and 


33a.     lo  muth  larvce  on  willow.     Photograph  by  M.V.  S. 


Nettling  Insects 


47 


even  com  leaves.     It  is  to  be  found  throughout  the  Eastern  and 
Southern  United  States. 

Automeris  io  is  the  best  kno\vn  of  the  nettling  caterpillars.     It  is 
the  larva  of  the  Io  moth,  one  of  the  Satumiidse.    The  mature  cater- 


336.     Io  moth.     Full  grown  larva.     Photograph  by  M.  V.  S. 


aSc.     Io  moth,     .'\dult.     Photograph  by  M.  V.  S. 

pillar,  (fig.  33),  which  reaches  a  length  of  two  and  one-half  inches,  is 
of  a  beautiful  pale  green  with  sublateral  stripes  of  cream  and  red  color 
and  a  few  black  spines  among  the  green  ones.  The  green  radiating 
spines  give  the  body  a  mossy  appearance.     They  are  tipped  with  a 


48 


Poisonous  Arthropods 


slender  chitinous  hair  whose  tip  is  readily  broken  off  in  the  skin  and 
whose  poisonous  content  causes  great  irritation.  Some  individuals 
are  very  susceptible  to  the  poison,  while  others  are  able  to  handle 
the  larvae  freely  without  any  discomfort.  The  larvae  feed  on  a  wide 
range  of  food  plants.  The}^  are  most  commonly  encountered  on 
com  and  on  willow,  because  of  the  opportunities  for  coming  in  contact 
with  them. 

The  larv^as  of  the  brown-tail  moth  (Euproctis  chrysorrhoea,)  (fig. 
35  and  36),  where  they  occur  in  this  countr\%  are,  on  account  of  their 
great  numbers,  the  most  serious  of  all  poisonous  caterpillars.     It  is 


35.     Larva  of  brown- tail  moth.     (Natural  size).     Photograph  by  M.  V.  S. 

not  necessary  here,  to  go  into  details  regarding  the  introduction  of 
this  species  from  Europe  into  the  New  England  States.  This  is  all 
available  in  the  literature  from  the  United  States  Bureau  of  Entomol- 
ogy and  from  that  of  the  various  states  which  are  fighting  the  species. 
Sujfifice  to  say,  there  is  every  prospect  that  the  pest  will  continue  to 
spread  throughout  the  Eastern  United  States  and  Canada  and  that 
wherever  it  goes  it  will  prove  a  direct  pest  to  man  as  well  as  to  his 
plants. 

Very  soon  after  the  introduction  of  the  species  there  occurred  in 
the  region  where  it  had  gained  a  foothold,  a  mysterious  dermatitis  of 
man.  The  breaking  out  which  usually  occurred  on  the  neck  or  other 
exposed  part  of  the  body  was  always  accompanied  by  an  intense 


Nettling  Insects  49 

itching.  It  was  soon  found  that  this  dermatitis  was  caused  by  certain 
short,  barbed  hairs  of  the  brown-tail  caterpillars  and  that  not  only  the 
caterpillars  but  their  cocoons  and  even  the  adult  female  moths  might 
harbor  these  nettling  hairs  and  thus  give  rise  to  the  irritation.  In 
many  cases  the  hairs  were  wafted  to  clothing  on  the  line  and  when  this 
was  worn  it  might  cause  the  same  trouble.  Still  worse,  it  was  found 
that  very  serious  internal  injury  was  often  caused  by  breathing  or 
swallowing  the  poisonous  hairs. 

The  earlier  studies  seemed  to  indicate  that  the  irritation  was 
purely  mechanical  in  origin,  the  result  of  the  minute  barbed  hairs 


36.      Browntail  moths.      One  male   and    two   females.       Photograph  by 
M.  V.  S. 

working  into  the  skin  in  large  numbers.  Subsequently,  however, 
Dr.  Tyzzer  (1907)  demonstrated  beyond  question  that  the  trouble 
was  due  to  a  poison  contained  in  the  hairs.  In  the  first  place,  it  is 
only  the  peculiar  short  barbed  hairs  which  will  produce  the  dermatitis 
when  rubbed  on  the  skin,  although  most  of  the  other  hairs  are  sharply 
barbed.  Moreover,  it  was  found  that  in  various  wa^^s  the  nettling 
properties  could  be  destroyed  without  modifying  the  structure  of  the 
hairs.  This  was  accompHshed  by  baking  for  one  hour  at  iio^  C,  by 
warming  to  60°  C  in  distilled  water,  or  by  soaking  in  one  per  cent,  or  in 
one-tenth  per  cent,  of  potassium  hydrate  or  sodium  hydrate.  The 
most  significant  part  of  his  work  was  the  demonstration  of  the  fact 


50 


Poisonous  Arthropods 


37 


that  if  the  netthng  hairs  are  mingled  with  blood,  they  immediately 
produce  a  change  in  the  red  corpuscles.     These  at  once  become 

coarsely   crenated,    and   the 
'  roleaux  are  broken  up  in  the 

\  vicinity  of  the  hair  (fig.  3  76) . 

The  corpuscles  decrease  in 
size,  the  coarse  crenations 
are  transformed  into  slender 
spines  which  rapidly  disap- 
pear, leaving  the  corpuscles 
in  the  form  of  spheres,  the 
light  refraction  of  which  con- 
trasts them  sharply  with  the 
normal  corpuscles.  The 
reaction  always  begins  at  the 

(a)  Ordinary  hairs  and  three  poison  hairs  of  sub-   ,  i      -u  •    4-      r  4-t,      t,    ;^ 

dorsal  and  lateral  tubercles  of  the  larva  of  the    Dasai  SHarp  pOmt  Ot  tnc  nair. 
browntail  moth.  Drawing  by  Miss  Kephart.  j^  ^^^^  ^^^  ^^    pfoduced  by 

purely  mechanical  means,  such  as  the  mingling  of  minute  par- 
ticles of  glass  wool,  the  barbed  hairs  of  a  tussock  moth,  or  the  other 
coarser  hairs  of  the  brown-tail,  with  the  blood. 

The  question  of  the  source  of  the  poison  has  been  studied  in  our 
laboratory  by  Miss  Cornelia 
Kephart.  She  first  confirmed 
Dr.  Tyzzer's  general  results 
and  then  studied  carefully  fixed 
specimens  of  the  larvae  to 
determine  the  distribution  of 
the  hairs  and  their  relation  to 
the  underlying  tissues. 

The  poison  hairs  (fig.  37), 
are  found  on  the  subdorsal 
and  lateral  tubercles  (fig.  38). 
in  bunches  of  from  three  to 
twelve  on  the  minute  papilla^ 
with  which  the  tubercles  are 
thickly  covered.  The  under- 
lying hypodermis  is  very 
greatly  thickened,  the  cells 
being  three  or  four  times  the  length  of  the  ordinary  hypodermal 
cells  and  being  closely  crowded  together.     Instead  of  a  pore  canal 


(b)   Effect  of  the  poison  on  the  blood  cor- 
puscles of  man.     After  Tyzzer. 


Nettling  Insects 


SI 


through  the  cuticula  for  each    individual  hair,  there  is  a  single  pore 
for  each  papillae   on  a  tubercle,  all  the  hairs  of  the  papilla  being 

connected  with  the 
underlying  cells 
through  the  same 
pore  canal,  (figs. 
39  and  40). 

The  hypodermis 
of  this  region  is  of 
two  distinct  types 
of  cells.  First, 
there  is  a  group  of 
slender  fusiform 
cells,  one  for  each 
poison  hair  on  the 
papilla,  which  are 
the  trichogen,  or 
hair-formative  cells.  They  are  crowded  to  one  side  and  towards 
the  basement  membrane  by  a  series  of  much  larger,  and  more  promi- 
nent cells  (fig.  40),  of  which  there  is  a  single  one  for  each  papilla. 
These  larger  cells  have  a  granular  protoplasm  with  large  nuclei  and 
are  obviously  actively  secreting.  They  are  so  characteristic  in 
appearance  as  to  leave  no  question  but  that  they  are  the  true 
poison  glands. 

Poisonous  lar^^ae  of  many  other  species  have  been  reported  from 
Europe  and  especially  from  the  tropics  but  the  above-mentioned 
species  are  the  more  important  of  those  occurring  in  the  United  States 
and  will  ser\'e  as  types.     It  should  be  noted  in  this  connection  that 


C  FK 

08.  Cross  section  of  the  larva  of  thebrowntail  moth  showing  the 
tubercles  bearing  the  poison  hairs.  Drawing  by  Miss 
Kephart. 


39      Epithelium  underlj  ing  poison  hairs  of  the  larva  of  the 
brow  ntail  moth.     Drawing  b>  Miss  Kephart. 


52 


Poisonous  Arthropods 


40.     Same  as  figure  39,  on  larger  scale. 


through  some  curious  mis- 
understanding Goeldi  (1913) 
has  featured  the  larva  of 
Orgyia  leucostigma,  the  white- 
marked  tussock  moth,  as  the 
most  important  of  the  poi- 
sonous caterpillars"  of  this 
country.  Though  there  are 
occasional  reports  of  irritation 
from  its  hairs  such  cases  are 
rare  and  there  is  no  evidence 
that  there  is  any  poison  pres- 
ent. Indeed,  subcutaneous 
implantation  of  the  hairs 
leads  to  no  poisoning,  but  merely  to  temporary  irritation. 

Occasionally,  the  hairs  of  certain  species  of  caterpillars  find  lodge- 
ment in  the  conjunctiva,  cornea,  or  iris  of  the  eye  of  man  and  give 
rise  to  the  condition  known  as  opthabma  nodosa.  The  essential 
feature  of  this  trouble  is  a  nodular  conjunctivitis  which  simtdates 
tuberculosis  of  the  conjunctiva  and  hence  has  been  called  psetido- 
tubercuJar.  It  may  be  distinguished  microscopically  by  the  presence 
of  the  hairs. 

Numerous  cases  of  opthalmia  nodosa  are  on  record.  Of  those 
from  this  country,  one  of  the  most  interesting  is  reported  by  de 
Schweinitz  and 
Shumway  (1904).  It 
is  that  of  a  child  of 
fifteen  years  whose 
eye  had  become  in- 
flamed owing  to  the 
presence  of  some  for- 
eign body.  Down- 
ward and  inward  on 
the  bulbar  conjunc- 
tiva were  a  number 
of  flattened,  grayish- 
yellow  nodules,  be- 
tween which  was  a 
marked  congestion  of 

+V,^   ^^♦-v:,,^^^;,^^!   ^.^A  41.     (a)   Nodular  conjunctivitis  in  the  eye  of  a  child. 

the   conjunctival  and  OeSchweinitz  and  Shumway. 


Nettling  Insects 


53 


416. 


Section  through  one  of  the  nodules  showing  the  cater- 
pillar hair.     DeSchweinitz  and  Shumway. 


episcleral  vessels  (fig.  41a).  Twenty-seven  nodules  could  be  differ- 
entiated, those  direct!}'  in  the  center  of  the  collection  being  some- 
what confluent  and 
assuming  a  crescen- 
tic  and  circular  ap- 
pearance. The  nod- 
ules were  excised 
and,  on  sectioning, 
were  found  to  be 
composed  of  a  layer 
of  spindle  cells  and 
round  cells,  outside 
of  which  the  tissue 
was  condensed  into 
a  capsule.  The 
interior  consisted  of 
epithelioid  cells,  be- 
tween which  was  a 
considerable  inter- 
cellular substance.  Directly  in  the  center  of  a  certain  number  of 
nodules  was  found  the  section  of  a  hair  (fig.  416).  The  evidence 
indicated  that  the  injury  had  resulted  from  playing  with  caterpillars 
of  one  of  the  Arctiid  moths,  Spilosoma  virginica.  Other  reported 
cases  have  been  caused  by  the  hairs  of  lar\'as  of  Lasiocampa  rubt, 
L.  pint,  Porthetria  dispar,  Psiliira  monacha  and  Cnethocampa 
processionea. 

Relief  from  Poisoning  by  Nettling  Larvae — The  irritation  from 
nettling  larv^a^  is  often  severe  and,  especially  in  regions  where  the 
brown-tail  abounds,  inquiries  as  to  treatment  arise.  In  general,  it 
may  be  said  that  cooling  lotions  afford  relief,  and  that  scratching, 
with  the  possibilities  of  secondary  infection,  shotdd  be  avoided,  in 
so  far  as  possible. 

Among  the  remedies  usually  at  hand,  weak  solutions  of  ammonia, 
or  a  paste  of  ordinary  baking  soda  are  helpful.  Castellani  and  Chalm- 
ers recommend  cleaning  away  the  hairs  by  bathing  the  region  with 
an  alkaline  lotion,  such  as  two  per  cent  solution  of  bicarbonate  of 
soda,  and  then  applying  an  ointment  of  ichthyol  (10%). 


54 


Poisonous  Arthropods 


In  the  brown-tail  district,  there  are  many  proprietary  remedies  of 
which  the  best  ones  are  essentially  the  following,  as  recommended 
by  Kirkland  (1907) : 

Carbolic  acid  }4  drachm. 

Zinc  oxide ^  oz. 

Lime  water 8  oz. 

Shake  thoroughly  and  rub  well  into  the  affected  parts. 

In  some  cases,  and  especially  where  there  is  danger  of  secondary 
infection,  the  use  of  a  weak  solution  of  creoline  (one  teaspoonful  to  a 
quart  of  water),  is  to  be  advised. 

Vescicating  Insects  and  those   Possessing  Other  Poisons  in 
THEIR  Blood   Plasma 

We  have  seen  that  certain  forms,  for  example,  the 
poisonous  spiders,  not  only  secrete  a  toxine  in  their 
poison  glands,  but  that  such  a  substance  may  be  ex- 
tracted from  other  parts  of  their  body,  or  even  their 
eggs.  There  are  many  insects  which  hkewise  possess  a 
42a.  Blister  bee-  poisouous  blood  plasma.  Such  forms  have  been  well 
designated  by  Taschenberg  as  cryptotoxic  (xpuxTOi;  = 
hidden).     We  shall  consider  a  few  representative  forms. 

The  Blister  Beetles — Fore- 
most among  the  cryptotoxic 
insects     are    the     MeloidcB    or 


"blister  beetles,"  to  which  the 
well-known  "Spanish  fly"  (fig. 
42a).  formerly  very  generally 
used  in  medical  practice,  be- 
longs. The  vescicating  property 
is  due  to  the  presence  in  the 
blood  plasma  of  a  peculiar, 
volatile,  crystalline  substance 
known  as  cantharidin,  which  is 
especially  abundant  in  the  repro- 
ductive organs  of  the  beetle.  Ac- 
cording to  Kobert,  the  amount 
of  this  varies  in  different  species 
from  .4  or  .5%  to  2.57%  of  the 
dry  weight  of  the  beetle. 


An  American  blister  beetle.     Meloe  an- 
gusticollis.     Photograph  by  M.  V.  S. 


Vescicating  Insects  55 

While  blister  beetles  have  been  especially  used  for  external  applica- 
tion, they  are  also  at  times  used  internally  as  a  stimulant  and  a 
diuretic.  The  powder  or  extract  was  formerly  much  in  vogue  as  an 
aphrodisiac,  and  formed  the  essential  constituent  of  various  philters, 
or  "love  powders".  It  is  now  known  that  its  effects  on  the  reproduc- 
tive organs  appear  primarily  after  the  kidneys  have  been  affected  to 
such  an  extent  as  to  endanger  life,  and  that  many  cases  of  fatal  poison 
have  been  due  to  its  ignorant  use. 

There  are  many  cases  on  record  of  poisoning  and  death  due  to 
internal  use,  and  in  some  instances  from  merely  external  application. 
There  are  not  rarely  cases  of  poisoning  of  cattle  from  feeding  on 
herbage  bearing  a  large  number  of  the  beetles  and  authentic  cases  are 
known  of  human  beings  who  have  been  poisoned  by  eating  the  flesh 
of  such  cattle.  Robert  states  that  the  beetles  are  not  poisonous  to 
birds  but  that  the  flesh  of  birds  which  have  fed  on  them  is  poisonous 
to  man,  and  that  if  the  flesh  of  chickens  or  frogs  which  have  fed  on 
the  cantharidin  be  fed  to  cats  it  causes  in  them  the  same  symptoms 
as  does  the  cantharidin. 

Treatment  of  cases  of  cantharidin  poison  is  a  matter  for  a  skilled 
physician.  Until  he  can  be  obtained,  emetics  should  be  administered 
and  these  should  be  followed  by  white  of  egg  in  water.  Oils  should 
be  avoided,  as  they  hasten  the  absorption  of  the  poison. 

Other  Cr3T)totoxic  Insects — -Though  the  blister  beetles  are  the 
best  known  of  the  insects  wdth  poisonous  blood  plasma,  various 
others  have  been  reported  and  we  shall  refer  to  a  few  of  the  best 
authenticated. 

One  of  the  most  famous  is  the  Chrysomelid  beetle,  Diamphidia 
simplex,  the  body  fluids  of  whose  larvse  are  used  by  certain  South 
African  bushmen  as  an  arrow  poison.  Its  action  is  due  to  the  presence 
of  a  toxalbimiin  which  exerts  a  hsemolytic  action  on  the  blood,  and 
produces  inflammation  of  the  subcutaneous  connective  tissue  and 
mucous  membranes.  Death  results  from  general  paralysis.  Krause 
(1907)  has  surmised  that  the  active  principle  may  be  a  bacterial  toxine 
arising  from  decomposition  of  the  tissues  of  the  lan^a,  but  he  presents 
no  support  of  this  view  and  it  is  opposed  by  all  the  available  evidence. 

In  China,  a  bug,  Heuckis  sanguinea,  belonging  to  the  family 
Cicadidae,  is  used  like  the  Meloidas,  to  produce  blistering,  and  often 
causes  poisoning.  It  has  been  assumed  that  its  vescicating  properties 
are  due  to  cantharidin,  but  the  presence  of  this  substance  has  not 
been  demonstrated. 


56  Poisonous  Arthropods 

Certain  Aphididae  contain  a  strongly  irritating  substance  which 
produces,  not  merely  on  mucous  membranes  but  on  outer  skin,  a 
characteristic  inflammation. 

It  has  been  frequently  reported  that  the  larvae  of  the  Eurpoean 
cabbage  butterfly,  Pieris  brassicce,  accidentally  eaten  by  cows,  horses, 
ducks,  and  other  domestic  animals,  cause  severe  colic,  attempts  to 
vomit,  paralysis  of  the  hind  legs,  salivation,  and  stomatitis.  On 
postmortem  there  are  to  be  found  hsemorrhagic  gastro-enteritis, 
splenitis,  and  nephritis.  Kobert  has  recently  investigated  the  subject 
and  has  found  a  poisonous  substance  in  the  blood  of  not  only  the 
larvae  but  also  the  pupae. 


CHAPTER   III 

PARASITIC  ARTHROPODA  AFFECTING  MAN 

The  relation  of  insects  to  man  as  simple  parasites  has  long  been 
■studied,  and  until  very  recent  years  the  bulk  of  the  literature  of  medi- 
cal entomology  referred  to  this  phase  of  the  subject.  This  is  now 
completely  overshadowed  by  the  fact  that  so  many  of  these  parasitic 
forms  are  more  than  simple  parasites,  they  are  transmitters  of  other 
microscopic  parasites  which  are  pathogenic  to  man.  Yet  the  impor- 
tance of  insects  as  parasites  still  remains  and  must  be  considered  in  a 
discussion  of  the  relation  of  insects  to  the  health  of  man.  In  taking 
up  the  subject  we  shall  first  consider  some  general  features  of  the 
phenomenon  of  animal  parasitism. 

Parasitism  is  an  adaptation  which  has  originated  very  often  among 
living  organisms  and  in  widely  separated  groups.  It  would  seem 
simple  to  define  what  is  meant  by  a  "parasite"  but,  in  reality,  the 
term  is  not  easily  limited.  It  is  often  stated  that  a  parasite  is  "An 
■organism  which  lives  at  the  expense  of  another,"  but  this  definition 
is  applicable  to  a  predatory  species  or,  in  its  broadest  sense,  to  all 
organisms.  For  our  purpose  we  may  say  with  Braun:  "A  parasite 
is  an  organism  which,  for  the  purpose  of  obtaining  food,  takes  up  its 
abode,  temporarily  or  permanently,  on  or  ^^^thin  another  living 
•organism". 

Thus,  parasitism  is  a  phase  of  the  broad  biological  phenomenon  of 
symbiosis,  or  living  together  of  organisms.  It  is  distinguished  from 
mutualism,  or  symbiosis  in  the  narrow  sense,  b}-  the  fact  that  only  one 
party  to  the  arrangement  obtains  any  advantage,  while  the  other  is 
to  a  greater  or  less  extent  injured. 

Of  parasites  we  may  distinguish  on  the  basis  of  their  location  on  or 
in  the  host,  ecto-parasites,  which  live  outside  of  the  body;  and  endo- 
parasites,  which  live  within  the  body.  On  account  of  their  method 
of  breathing  the  parasitic  arthropods  belong  almost  exclusively  to  the 
first  of  these  groups. 

On  the  basis  of  relation  to  their  host,  we  find  temporary  parasites, 
those  which  seek  the  host  only  occasionally,  to  obtain  food;  and  the 
stationary  or  permanent  parasites  which,  at  leavSt  during  certain  stages, 
do  not  leave  their  host. 

Facultative  parasites  are  forms  which  are  not  normally  parasitic, 
but  which,  when  accidentally  ingested,  or  otherwise  brought  into  the 


58  Parasitic  Arthropods 

body,  are  able  to  exist  for  a  greater  or  less  period  of  time  in  their 
unusual  environment.  These  are  generally  called  in  the  medical 
literature  "pseudoparasites"  but  the  term  is  an  unfortunate  one. 

We  shall  now  take  up  the  different  groups  of  arthropods,  discussing 
the  more  important  of  the  parasitic  forms  attacking  man.  The 
systematic  relationship  of  these  forms,  and  key  for  determining 
important  species  will  be  found  in  Chapter  XII. 

AcAKiNA  OR  Mites 

The  Acarina,  or  mites,  form  a  fairly  natural  group  of  arachnids, 
characterized,  in  general,  by  a  sac-like,  unsegmented  body  which  is 
generally  fused  with  the  cephalothorax.  The  mouth-parts  have  been 
united  to  from  a  beak  or  rostrum. 

The  representatives  of  this  group  undergo  a  marked  metamor- 
phosis. Commonly,  the  lar\^ffi  on  hatching  from  the  egg,  possess  but 
three  pairs  of  legs,  and  hence  are  called  hexapod  larva.  After  a  molt, 
they  transfonri  into  nymphs  which,  like  the  adult,  have  four  pairs  of 
legs  and  are  called  octopod  nymphs.  These  after  a  period  of  growth, 
molt  one  or  more  times  and,  acquiring  external  sexual  organs,  become 
adult. 

Most  of  the  mites  are  free-living,  but  there  are  many  parasitic 
species  and  as  these  have  originated  in  widely  separated  families,  the 
Acarina  form  an  especially  favorable  group  for  study  of  the  origin  of 
parasitism.  Such  a  study  has  been  made  by  Ewing  (191 1),  who  has 
reached  the  following  conclusions: 

"We  have  strong  evidence  indicating  that  the  parasitic  habit  has 
originated  independently  at  least  eleven  times  in  the  phylogeny  of  the 
Ararina.  Among  the  zoophagous  parasites,  the  parasitic  habit  has 
been  developed  from  three  different  types  of  free-living  Acarina: 
(a)  predaceous  forms,  (b)  scavengers,  (c)  forms  living  upon  the  juices 
of  plants." 

Ewing  also  showed  that  among  the  living  forms  of  Acarina  we  can 
trace  out  all  the  stages  of  advancing  parasitism,  semiparasitism, 
facultative  parasitism,  even  to  the  fixed  and  permanent  type,  and 
finally  to   endoparasitism. 

Of  the  many  parasitic  forms,  there  are  several  species  which  are 
serious  parasites  of  man  and  we  shall  consider  the  more  important  of 
these.     Infestation  by  mites  is  technically  known  as  acariasis. 


Acarina,  or  Mites 


59 


43.     Effect  of  the  harvest  inites  on  the   skin  of  man.     Photograph   by 
J.  C.  Bradley. 


'6o 


Parasitic  Arthropods 


The  Trombidiidae,  or  Harvest  Mites 

In  many  parts  of  this  country  it  is  impossible  for  a  visitor  to  go 
into  the  fields  and,  particularly,  into  berry  patches  and  among  tall 
weeds  and  grass  in  the  summer  or  early  fall  withQut  being  affected  by 
an  intolerable  itching,  which  is  followed,  later,  by  a  breaking  out  of 
wheals,  or  papules,  surrounded  by  a  bright  red  or  violaceous  aureola, 
(fig.  43).  It  is  often  regarded  as  a  urticaria  or  eczema,  produced  by 
•change  of  climate,  an  error  in  diet,  or  some  condition  of  general  health. 
Sooner  or  later,  the  victim  finds  that  it  is  due  to  none  of  these,  but 
to  the  attacks  of  an  almost  microscopic  red  mite,  usually  called 
"jigger"  or  "chigger"  in  this  country.  As  the  term  "chigger"  is 
applied  to  one  of  the  true  fleas,  Dermatophilus  penetrans,  of  the  tropics, 

these  forms  are  more 
correctly  known  as 
"harvest  mites." 
Natives  of  an  infested 
region  may  be  so 
immune  or  accus- 
tomed to  its  attacks 
as  to  be  unaware  of 
its  presence,  though 
such  immunity  is  by 
no  means  possessed 
by  all  who  have  been 
long  exposed  to  the 
annoyance. 
The  harvest  mites,  or  chiggers,  attacking  man  are  larval  forms, 
possessing  three  pairs  of  legs  (fig.  44).  Their  systematic  position  was 
at  first  unknown  and  they  were  classed  under  a  special  genus  Leptus, 
a  name  which  is  very  commonly  still  retained  in  the  medical  literature. 
It  is  now  known  that  they  are  the  larval  forms  of  various  species  of 
the  genus  Trombidium,  a  group  of  predaceous  forms,  the  adults  of 
which  feed  primarily  on  insects  and  their  eggs.  In  this  country  the 
species  best  known  are  those  to  be  found  late  in  summer,  as  larvae 
at  the  base  of  the  wings  of  houseflies  or  grasshoppers. 

There  is  much  uncertainty  as  to  the  spec'es  of  the  larvae  attacking 
man  but  it  is  clear  that  several  are  implicated.  Bruyant  has  shown 
that  in  France  the  larvas  Trombidium  inapinaium  and  Trombidium 
holosericeum  are  those  most  frequently  found.  The  habit  of  attacking 
man  is  abnormal  and  the  larvae  die  after  entering  the  skin.  Normally 
they  are  parasitic  on  various  insects. 


44.     Harvest  mites.     (Lai vae  of  Trombidium).     After  C.  V. 
Riley. 


The  Harvest  Mites  6i 

Most  recent  writers  agree  that,  on  man,  they  do  not  bore  into  the 
skin,  as  is  generally  supposed,  but  enter  a  hair  follicle  or  sebaceous 
gland  and  from  the  bottom  of  this,  pierce  the  cutis  with  their  elongate 
hypopharynx.  According  to  Braun,  there  arises  about  the  inserted 
hypopharynx  a  fibrous  secretion — the  so-called  "beak"  which  is,  in 
reahty,  a  product  of  the  host.  Dr.  J.  C.  Bradley,  however,  has  made 
careful  observations  on  their  method  of  attack,  and  he  assures  us  that 
the  mite  ordinarily  remains  for  a  long  time  feeding  on  the  surface  of 
the  skin,  where  it  produces  the  erythema  above  described.  During 
this  time  it  is  not  buried  in  the  skin  but  is  able  to  retreat  rapidly  into 
it  through  a  hair  follicle  or  sweat  gland.  The  irritation  from  the 
mites  ceases  after  a  few  days,  but  not  infrequently  the  intolerable 
itching  leads  to  so  much  scratching  that  secondary  infection  follows. 

Relief  from  the  irritation  may  be  afforded  by  taking  a  warm  salt 
bath  as  soon  as  possible  after  exposure  or  by  killing  the  mites  by 
application  of  benzine,  sulphur  ointment  or  carbolized  vaseline. 
When  they  are  few  in  number,  they  can  be  picked  out  with  a  sterile 
needle. 

Much  may  be  done  in  the  way  of  warding  off  their  attacks  by 
wearing  gaiters  or  close-woven  stockings  extending  from  ankle  to  the 
knee.  Still  more  efficacious  is  the  sprinkling  of  flowers  of  sulphur  in 
the  stockings  and  the  underclothes  from  a  little  above  the  knee,  down. 
The  writers  have  known  this  to  make  it  possible  for  persons  who  were 
especially  susceptible  to  work  with  perfect  comfort  in  badly  infested 
regions.  Powdered  naphthalene  is  successfully  used  in  the  same  way 
and  as  Chittenden  (1906)  points  out,  is  a  safeguard  against  various 
forms  of  man -infesting  tropical  insect  pests. 

*  The  question  of  the  destruction  of  the  mites  in  the  field  is  some- 
times an  important  one,  and  under  some  conditions,  is  feasible. 
Chittenden  states  that  much  can  be  accomplished  by  keeping  the 
grass,  weeds,  and  useless  herbage  mowed  closely,  so  as  to  expose  the 
mites  to  the  sun.  He  believes  that  in  some  cases  good  may  be  done 
by  dusting  the  grass  and  other  plants,  after  cutting,  with  flowers  of 
stdphur  or  by  spraying  with  dilute  kerosene  emulsion  in  which 
sulphur  has  been  mixed.  More  recently  (1914)  he  calls  attention  to 
the  value  of  cattle,  and  more  especially  sheep,  in  destroying  the  pests 
by  tramping  on  them  and  by  keeping  the  grass  and  herbage  closely 
cropped. 


62 


Parasitic  Arthropods 


IXODOIDEA   OR   TiCKS 

Until  recently,  the  ticks  attracted  comparatively  little  attention 
from  entomologists.     Since  their  importance  as  carriers   of  disease 

has  been  established,  interest  in 

\ylnternal  I  ^/o? '',' 
/  \ hypoito'T'e 


Palp  arlicte4 
Art.  3 


Shaft  0' 
Chilice'-a 


Argus   persicus.     Capitulum  of  male 
After  Nuttall  and  Warburton. 


the  group  has  been  enormously 
stimulated  and  now  they  rank 
second  only  to  the  mosquitoes 
in  the  amount  of  detailed  study 
that  has  been  devoted  to  them. 
The  ticks  are  the  largest  of 
the  Acarina.  They  are  char- 
acterized by  the  fact  that  the 
hypostome,  or  "tongue"  (fig.  45) 
is  large  and  file-like,  roughened 
by  sharp  teeth.  They  possess 
a  breathing  pore  on  each  side 
of  the  body,  above  the  third 
or  fourth  coxae  (fig.  456). 

There  are  two  distinct  fami- 
lies of  the  Ixodoidea,  differing 
greatly  in  structure,  life-history  and  habits.  These  are  the  Argasidae 
and  the  Ixodidae.  We  shall  follow  Nuttall  (1908)  in  characterizing 
these  two  families  and  in  pointing  out  their  biological  differences,  and 
shall  discuss  briefly  the  more  important  species  which  attack  man. 
The  consideration  of  the 
ticks  as  carriers  of  disease 
will  be  reserved  for  a  later 
chapter. 

Argasidae 

In  the  ticks  belonging  to 
the  famih'  Argasidae,  there 
is  comparati\-ely  little  sexual 
dimorphism,  while  this  is 
very  marked  in  the  Ixodidee. 
The  capitulum,  or  so-called 
"head"  is  ventral,  instead  of 
terminal;  the  palpi  are  leg- 
like, with  the  segments  subequal;  the  scutum,  or  dorsal  shield,  is 
absent;  eyes,  when  present,  are  lateral,  on  supracoxal  folds.     The 


456. 


Left  spiracle  of  n>Tnph  of  Argas  persicus. 

After  Nuttall  and  Warburton. 


Ixodoidea,  or  Ticks 


63 


■spiracles  are  very  small;  coxae  unarmed;  tarsi  without  ventral  spurs, 
and  the  pulvilli  are  absent  or  rudimentary. 

In  habits  and  life  history  the  Argasidas  present  striking  characteris- 
tics. In  the  first  place,  they  are  long-lived,  a  factor  which  counts  for 
much  in  the  maintenance  of  the  species.  They  are  intermittent 
feeders,  being  comparable  with  the  bed-bug  in  this  respect.  There  are 
two  or  more  nymphal  stages,  and  they  may  molt  after  attaining  matu- 
rity.    The  female  lays  comparatively  few  eggs  in  several  small  batches . 

Nuttall  (191 1)  concludes  that  "The  Argasidae  represent  the  rela- 
tiveh'  primitive  type  of  ticks  because  they  are  less  constantly  para- 


46.     Argus  persicus.     Dorsal  and  ventral  aspects.     (X4).     After  Hassell. 


sitic  than  are  the  Ixodidae.  Their  nymphs  and  adults  are  rapid 
feeders  and  chiefly  infest  the  habitat  of  their  hosts.  *  *  *  Owing 
to  the  Argasidce  infesting  the  habitats  of  their  hosts,  their  resistance 
to  prolonged  starvation  and  their  rapid  feeding  habits,  they  do  not 
need  to  bring  forth  a  large  progeny,  because  there  is  less  loss  of  life 
in  the  various  stages,  as  compared  with  the  Ixodidae,  prior  to  their 
attaining  maturity." 

Of  the  Argasidae,  we  have  in  the  United  States,  several  species 
which  have  been  reported  as  attacking  man. 

Argas  persicus,  the  famous  "  Miana  bug"  (fig.  46),  is  a  very  widely 
distributed  species,  being  reported  from  Europe,  Asia,  Africa,  and 
Australia.     It    is    everywhere    preeminently    a    parasite    of    fowls. 


64 


Parasitic  Arthropods 


According  to  Nuttall  it  is  specifically  identical  with  Argas  americanus' 
Packard  or  Argas  miniatus  Koch,  which  is  commonly  found  on  fowls- 

in  the  United  States,  in  the  South 
and  Southwest.  Its  habits  are  com- 
parable to  those  of  the  bed-bug.  It 
feeds  intermittently,  primarily  at 
night,  and  instead  of  remaining  on  its- 
host,  it  then  retreats  to  cracks  and 
crevices.  Hunter  and  Hooker  (1908) 
record  that  they  have  found  the  larva 
to  remain  attached  for  five  or  eight 
days  before  dropping.  Unlike  the- 
Ixodidas,  the  adults  oviposit  fre- 
quently. 

The  most  remarkable  feature  of 
the  biology  of  this  species  is  the  great 
47.  otiobius  (Ornithodoros)  megnini.  head  longevity,   especially    of    the    adult. 

of  nymph,     After  Stiles.  o  j  '  r-  j 

Hunter  and  Hooker  report  keeping 
larvae  confined  in  simimer  in  pill  boxes  immediately  after  hatch- 
ing for  about  two  months  while  under  similar  conditions  those- 
of  the  Ixodid,  Boophilus  annulatus  lived  for  but  two  or  three  days.. 


48.     Otiobius  (Ornithodoros)  megnini,  male,     (a)  dorsal,  (6)  ventral 
aspect.     After  Nuttall  and  Warburton. 


Many  writers  have  recorded  keeping  adults  for  long  periods  without' 
food.  We  have  kept  specimens  in  a  tin  box  for  over  a  year  and  a  half 
and  at  the  end  of  that  time  a  number  were  still  alive.  Laboulliene 
kept  unfed  adults  for  over  three  years.     In  view  of  the  effectiveness  of 


Ixodoidea,  or  Ticks  65 

sulphur  in  warding  off  the  attacks  of  Trombidiida},  it  is  astonishing 
to  find  that  Lounsbury  has  kept  adults  of  Argas  persicus  for  three 
months  in  a  box  nearly  filled  with  flowers  of  sulphur,  with  no  apparent 
effect  on  them. 

We  have  already  called  attention  to  the  occasional  serious  effects 
of  the  bites  of  this  species.  While  such  reports  have  been  frequently 
discredited  there  can  be  no  doubt  that  they  have  foundation  in  fact. 
The  readiness  with  which  this  tick  attacks  man,  and  the  extent  to 
which  old  huts  may  be  infested  makes  it  especially  troublesome. 

Otiobius  {Ornithodoros)  megnini,  the "spinose  ear-tick  "(figs.  47, 48), 
first  described  from  Mexico,  as  occurring  in  the  ears  of  horses,  is  a 
common  species  in  our  Southwestern  States  and  is  recorded  by  Banks 
as  occurring  as  far  north  as  Iowa. 

The  species  is  remarkable  for  the  great  dift'erence  between  the 
spiny  nymph  stage  and  the  adult.  The  life  history  has  been  worked 
out  by  Hooker  (1908).  Seed  ticks,  having  gained  entrance  to  the 
ear,  attach  deeply  down  in  the  folds,  engorge,  and  in  about  five  days, 
molt ;  as  nymphs  with  their  spinose  body  they  appear  entirely  unlike 
the  lar\'se.  As  nymphs  they  continue  feeding  sometimes  for  months. 
Finally  the  nymph  leaves  the  host,  molts  to  form  the  unspined  adult, 
and  without  further  feeding  is  fertilized  and  commences  oviposition. 

The  common  name  is  due  to  the  fact  that  in  the  young  stage  the 
ticks  occur  in  the  ear  of  their  hosts,  usually  horses  or  cattle.  Not 
uncommonly  it  has  been  reported  as  occurring  in  the  ear  of  man  and 
causing  verv'  severe  pain.  Stiles  recommends  that  it  be  removed  by 
pouring  some  bland  oil  into  the  ear. 

Banks  (1908)  reports  three  species  of  Ornithodoros — O.  turicata, 
coriaceus  and  talaje — as  occurring  in  the  United  States.  All  of  these 
attack  man  and  are  capable  of  inflicting  very  painful  bites. 

Ixodidae 

The  ticks  belonging  to  the  family  Ixodidae  (figs.  49  and  50)  exhibit 
a  marked  sexual  dimorphism.  The  capitulum  is  anterior,  terminal, 
instead  of  ventral  as  in  the  Argasid^e;  the  palpi  are  relatively  rigid 
(except  in  the  subfamily  Ixodina^),  with  rudimentary  fourth  segment; 
scutum  present;  eyes,  when  present,  dorsal,  on  side  of  scutum.  The 
spiracles  are  generally  large,  situated  well  behind  the  fourth  coxae; 
coxse  generally  wdth  spurs;  pulvilli  always  present. 

In  habits  and  life  history  the  typical  Ixodidae  differ  greatly  from 
the  Argasida).     They  arc  relatively  short-lived,  though  some  recent 


66 


Parasitic  Arthropods 


Ixodes  ricinus;  male,  ventral  aspert.     After 
Braun  and  Luehe. 


work  indicates  that  their  long- 
evity has  been  considerably 
under-estimated.  Typically, 
they  are  permanent  feeders, 
remaining  on  the  host,  or  hosts, 
during  the  greater  part  of  their 
life.  They  molt  twice  onl}^ 
on  leaving  the  larval  and  the 
nymphal  stages.  The  adult 
female  deposits  a  single,  large 
batch  of  eggs.  Contrasting 
the  habits  of  the  Ixodidse  to 
those  of  the  Argasida?,  Nuttall 
(191 1)  emphasizes  that  the 
Ixodidas  are  more  highly 
specialized  parasites.  "The 
majority  are  parasitic  on  hosts 
having  no  fixed  habitat  and 
consequently  all  stages,  as  a 
rule,  occur  upon  the  host." 
As  mere  parasites  of  man,  apart  from  their  power  to  transmit 

disease,  the  Ixodidse  are  much  less  important  than  the  Argasidse. 

Many  are  reported  as  occasionally  attacking  man  and  of  these  the 

folloAving  native    spe- 
cies may  be  mentioned. 
Ixodes  riciwiis,  the 

European  castor  bean 

tick  (figs.  49,  50),  is  a 

species  which  has  been 

often    reported    from 

this  country  but  Banks 

(1908)  has  shown  that, 

though  it   does  occur, 

practically    all   of  the 

records  apply  to  Ixodes 

scaptdaris    or    Ixodes 

cookei.       In     Europe, 

Ixodes  ricinus  is  very 

1  1        ,  1  .50.     Ixodes  ricinus,  var.  seapularis,  female.     Capitulum  and 

aDUnOant      anCl       very  scutum;    ventral  aspect   of   capitulum;  coxae;  tarsus  4; 

1  ,  ,       1  spiracle;  genital  and  anal  grooves.     After    Nuttall  and 

commonly     attacks  warburton. 


Ixodoidea,  or  Ticks  67 

man.  At  the  point  of  penetration  of  the  hypostome  there  is  more  or 
less  inflammation  but  serious  injury  does  not  occur  unless  there  have 
been  introduced  pathogenic  bacteria  or,  unless  the  tick  has  been 
abruptly  removed,  leaving  the  capitulum  in  the  wound.  Under  the 
latter  circumstances,  there  maybe  an  abscess  fonned  about  the  foreign 
body  and  occasionally,  serious  results  have  followed.  Under  certain 
conditions  the  tick,  in  various  stages,  may  penetrate  under  the  skin 
and  produce  a  tumor,  within  which  it  may  survive  for  a  considerable 
period  of  time. 

Ixodes  cookei  is  given  by  Banks  as  "common  on  mammals  in  the 
Eastern  States  as  far  west  as  the  Rockies."  It  is  said  to  affect  man 
severely. 

Amhlyomma  americanum,  (fig.  i58e),  the  "lone  star  tick,"  is 
wideh'  distributed  in  the  United  States.  Its  common  name  is  derived 
from  the  single  silvery  spot  on  the  scutum  of  the  female.  Hunter 
and  Hooker  regard  this  species  as,  next  to  Boophilus  annulatus,  the 
most  important  tick  in  the  United  States.  Though  more  common  on 
cattle,  it  appears  to  attack  mammals  generally,  and  "in  portions  of 
Louisiana  and  Texas  it  becomes  a  pest  of  considerable  importance  to 
moss  gatherers  and  other  persons  who  spend  much  time  in  the  forests." 

Amblyouima  cajennoise,  noted  as  a  pest  of  man  in  central  and 
tropical  America,  is  reported  from  various  places  in  the  south  and 
southwestern  United  States. 

Dermaccntor  variabilis  is  a  common  dog  tick  of  the  eastern  United 
States.  It  frequently  attacks  man.  but  the  direct  effects  of  its  bite 
are  negligible. 

The  "  Rocky  Mountian  spotted  fever  tick"  {Dermacentor  andersoni 
according  to  Stiles,  D.  venushis  according  to  Banks)  is,  from  the  view- 
point of  its  effects  on  man,  the  most  important  of  the  ticks  of  the 
United  States.  This  is  because,  as  has  been  clearly  established,  it 
transmits  the  so-called  "spotted  fever"  of  man  in  our  northwestern 
states.  This  phase  of  the  subject  will  be  discussed  later  and  it  need 
merely  be  mentioned  here,  that  this  species  has  been  reported  as 
causing  painful  injuries  by  its  bites.  Dr.  Stiles  states  that  he  has 
seen  cases  of  rather  severe  lymphangitis  and  various  sores  and  swell- 
ings developing  from  this  cause.  In  one  case,  of  an  individual  bitten 
near  the  elbow,  the  arm  became  very  much  swollen  and  the  patient 
was  confined  in  bed  for  several  days.  The  so-called  tick  paralysis 
produced  b>'  this  species  is  discussed  in  a  preceding  chapter. 


68 


Parasitic  Arthropods 


There  arc  many  other  records  of  various  species  of  ticks  attacking 
man,  but  the  above-mentioned  will  serv^e  as  typical  and  it  is  not  neces- 
sary to  enter  into  greater  detail. 

Treatment  of  Tick  Bites — When  a  tick  attaches  to  man  the  first 
thing  to  be  done  is  to  remove  it  without  leaving  the  hypostome  in  the 
wound  to  fester  and  bring  about  secondary'  effects.  This  is  best 
accomplished  by  applying  to  the  tick's  body  some  substance  which 
will  cause  it  to  more  readily  loosen  its  hold.     Gasoline  or  petroleum, 

oil  or  vaseline  will  sen^e. 
For  removing  the 
spinose  ear-tick,  Stiles 
recommends  pouring 
some  bland  oil  into  the 
ear.  Others  have  used 
effectively  a  pledget  of 
cotton  soaked  in  chloro- 
form. 

In  general,  the  treat- 
ment recommended  b\' 
Wellman  for  the  bites 
of  Ornithodoros  moubata 
^vill  prove  helpful.  It 
consists  of  prolonged 
bathing  in  ^-ery  hot 
water,  followed  by  the 
application  of  a  strong 
solution  of  bicarbonate 
of  soda,  which  is  allowed  to  dry  upon  the  skin.  He  states  that  this 
treatment  is  comforting.  For  severe  itching  he  advises  smearing 
the  bites  with  vaseline,  which  is  slightly  impregnated  with  camphor 
or  menthol.  Medical  aid  should  be  sought  when  complications  arise. 
The  Dermanyssidae  are  Gamasid  mites  which  differ  from  others  of 
the  group  in  that  they  are  parasitic  on  vertebrates.  None  of  the 
species  normally  attack  man,  but  certain  of  them,  especially  the 
poultry  mite,  may  be  accidental  annoyances. 

Dermanyssus  gallin(s  (fig.  51),  the  red  mite  of  poultry,  is  an  exceed- 
ingly common  and  widespread  parasite  of  fowls.  During  the  day 
it  lives  in  cracks  and  crevices  of  poultry  houses,  under  supports  of 
roosts,  and  in  litter  of  the  food  and  nests,  coming  out  at  night  to  feed. 


Dermanyssus  galHnae,  female.     After  Delafond. 


TarsonemidcB 


69 


Pediculoides    ventricosus, 
male.     After  Webster. 


They  often  attack  people  working  in  poiiltry  houses  or  handling  and 
plucking  infested  fowls.  They  may  cause  an  intense  pruritis,  but  they 

do  not  produce  a  true  dermatosis,  for 
they  do  not  find  conditions  favorable  for 
multiplication  on  the  skin  of  man. 

Tarsonemidae 

The  representatives  of  the  family  Tar- 
sonemidaB  are  minute  mites,  with  the  body 
di\-ided  into  cephalothorax  and  abdomen. 
There  is  marked  sexual  dimorphism. 
The  females  possess  stigmata  at  the 
anterior  part  of  the  body,  at  the  base  of 
the  rostrum,  and  differ  from  all  other  mites 
in  having  on  each  side,  a  prominent  clavate 
organ  between  the  first  and  second  legs. 
The  larva,  when  it  exists,  is  hexapodous 
and  resembles  the  adult.     A  number  of  the 

species  are  true  parasites  on  insects,  while   others   attack  plants. 

Several  of  them  may  be  accidental  parasites  of  man. 
Pediculoides    ventricosus 

(fig.  52  and  53)  is,  of  all  the 

Tarsonemidae    reported,    the 

one  which  has  proved  most 

troublesome  to  man.     It  is  a 

predaceous     species      which 

attacks  a    large   number   of 

insects  but  which  has  most 

commonly  been  met  with  by 

man  through  its  fondness  for 

certain  grain -infesting  insects, 

notably  the  Angoumois  grain 

moth,  Sitotroga  cerealella,  and 

the  wheat  straw-worm,  Iso- 

soma  grande.     In  recent  years 

it  has  attracted  much  atten- 
tion in  the  United  States  and 

its    distribution    and   habits 

have  been  the  object  of  detail- 
ed study  by  Webster  (1901).  '^-    "^A^e^'webstlr."'"""''  ^""'"'  ''""'''  ^"^  ^^^ 


70 


Parasitic  Arthropods 


There  is  a  very  striking  sexual  dimorphism  in  this  species.  The 
non-gravid  female  is  elongate,  about  2oo[i.  by  70[jl  (fig.  52),  with  the 
abdomen  slightly  striated  longitudinally.  The  gravid  female  (fig.  53) 
has  the  abdomen  enormously  swollen,  so  that  it  is  from  twenty  to  a 
hundred  times  greater  than  the  rest  of  the  body.  The  species  is 
viviparous  and  the  larvae  undergo  their  entire  growth  in  the  body  of 
the  mother.  They  emerge  as  sexually  mature  males  and  females 
which  soon  pair.     The  male  (fig.   54)  is  much  smaller,  reaching  a 

length  of  only  320^  but 
is  relatively  broad, 
8c\j.,  and  angular.  Its 
abdom'enis  very  great- 
ly reduced. 

As  far  back  as  1850 
it  was  noted  as  caus- 
ing serious  outbreaks 
of  peculiar  dermatitis 
among  men  handling 
infested  grain.  For 
some  time  the  true 
source  of  the  difficulty 
was  unknown  and  it 
was  even  believed  that 
the  grain  had  been 
p  oisoned .  Webster 
has  shown  that  in  this 
country  (and  probably 
in  Europe  as  well)  its 
attacks  have  been  mistaken  for  those  of  the  red  bugs  or  "chiggcrs" 
(larval  Trombiidas).  More  recently  a  number  of  outbreaks  of  a 
mysterious  "skin  disease"  were  traced  to  the  use  of  straw  mattresses, 
which  were  found  to  be  swarming  with  these  almost  microscopic 
forms  which  had  turned  their  attentions  to  the  occupants  of  the  beds. 
Other  cases  cited  were  those  of  farmers  running  wheat  through  a 
fanning  mill,  and  of  thrashers  engaged  in  feeding  unthrashed  grain 
into  the  cylinder  of  the  machine. 

The  medical  aspects  of  the  question  have  been  studied  especially 
by  Schamberg  and  Goldberger  and  from  the  latter 's  summary  (19 10) 
we  derive  the  following  data.  Within  twe  ve  to  sixteen  hours  after 
exposure,  itching  appears  and  in  severe  cases,  especially  where  expo- 


54.     Pediculoides  ventricosus,  male.     After  Braun. 


Pediculoides  Ventricosus 


71 


sure  is  continued  night  after  night  by  sleeping  on  an  infested  bed,  the 
itching  may  become  almost  intolerable.  Simultaneously,  there 
appears  an  eruption  which  characteristically  consists  of  wheals 
surrounded  by  a  vesicle  (fig.  55).  The  vesicle  as  a  rule  does  not  exceed 
a  pin  head  in  size  but  ma}^  become  as  large  as  a  pea.     Its  contents 


55. 


Lesions  produced  by  the  attacks  of  Pediculoides  ventri- 
cosus.    After  Webster. 


rapidly  become  turbid  and  in  a  few  hours  it  is  converted  into  a  pustule. 
The  eruption  is  most  abundant  on  the  trunk,  slight  on  the  face  and 
extremities  and  almost  absent  on  the  feet  and  hands.  In  severe  cases 
there  may  be  constitutional  disturbances  marked,  at  the  outset,  by 
chilliness,  nausea,  and  vomiting,  followed  for  a  few  days  by  a  slight 
elevation  of  temperature,  with  the  appearance  of  albumin  in  the 
urine.  In  some  cases  the  eruj^tion  may  simulate  that  of  chicken-pox 
or  small-pox. 


72  Parasitic  Arthropods 

Treatment  for  the  purpose  of  killing  the  mites  is  hardly  necessary 
as  they  attach  feebh^  to  the  surface  and  are  readily  brushed  oflf  by 
friction  of  the  clothes.  "Antipruritic  treatment  is  always  called  for; 
warm,  mildly  alkaline  baths  or  some  soothing  ointment,  such  as  zinc 
oxide  will  be  found  to  fulfil  this  indication."  Of  course,  reinfestation 
must  be  guarded  against,  by  discarding,  or  thoroughly  fumigating 
infested  mattresses,  or  by  avoiding  other  sources.  Goldbcrger  sug- 
gests that  farm  laborers  who  must  work  with  infested  wheat  or  straw 
might  protect  themselves  by  anointing  the  bod}-  freely  with  some 
bland  oil  or  grease,  followed  by  a  change  of  clothes  and  bath  as  soon 
as  their  work  is  done.  We  are  not  aware  of  any  experiments  to 
determine  the  effect  of  flowers  of  sulphur,  but  their  efficiency  in  the 
case  of  "red  bugs"  suggests  that  they  are  worth  a  trial  against 
Pediculoides. 

Various  species  of  Tjrrogljrphidae  (fig.  150/)  may  abound  on  dried 
fruits  and  other  products  and  attacking  persons  handling  them,  may 
cause  a  severe  dermatitis,  comparable  to  that  described  above  for 
Pediculoides  ventricosus.  Many  instances  of  their  occurrence  as  such 
temporary  ectoparasites  are  on  record.  Thus,  workers  who  handle 
vanilla  pods  are  subject  to  a  severe  dermatitis,  known  as  vanillism, 
which  is  due  to  the  attacks  of  Tyroglyphus  siro,  or  a  closely  related 
species.  The  so-called  "grocer's  itch"  is  similarly  caused  by  mites 
infesting  various  products.  Castellani  has  shown  that  in  Ceylon, 
workers  employed  in  the  copra  mills,  where  dried  cocoanut  is  ground 
up  for  export,  are  much  annoyed  by  mites,  which  yjroduce  the  so-called 
"copra  itch."  The  skin  of  the  hands,  arms  and  legs,  and  soinetimes 
of  the  whole  body,  except  the  face,  is  covered  by  fairly  numerous,  very 
pruriginous  papules,  often  covered  by  small,  bloody  crusts  due  to 
scratching.  The  condition  is  readily  mistaken  for  scabies.  It  is 
due  to  the  attacks  of  Tyroglyphus  longior  castellanii  which  occur  in 
enormous  numbers  in  some  samples  of  the  copra. 

Sarcoptidae 

The  Sarcoptidae  are  minute  whitish  mites,  semi-globular  in  shape, 
with  a  delicate  transversely  striated  cuticula.  They  lack  eyes  and 
tracheae.  The  mouth-parts  are  fused  at  the  base  to  form  a  cone 
which  is  usually  designated  as  the  head.  The  legs  are  short  and 
stout,  and  composed  of  five  segments.  The  tarsi  may  or  may  not 
possess  a  claw  and  may  terminate  in  a  pedunculated  sucker,  or  simple 
long  bristle,  or  both.     The  presence  or  absence  of  these  structures 


SarcopiidcB,  or  Itch  Mites 


73 


oOa. 


Sarcoptes  scabiei,  male. 
(X  100).  After  Fiirsten- 
berg. 


and  their  distribution  arc  much  used  in  classification.     The  mites 

live  on  or  under  the  skin  of  mammals  and  birds,  where  they  produce 

the  disease  known  as  scabies,  mange,  or 
itch.  Several  species  of  the  Sarcoptidae 
attack  man  but  the  most  important  of 
these,  and  the  one  pre-eminent  as  the 
"itch  mite"  is  Sarcoptes  scabiei. 

The  female  of  Sarcoptes  scabiei,  of  man, 
is  oval  and  yellowish  white;  the  male 
more  rounded  and  of  a  somewhat  reddish 
tinge,  and  much  smaller.  The  body  is 
marked  by  transverse  striae  which  are 
partly  interrupted  on  the  back.  There 
are  transverse  rows  of  scales,  or  pointed 
spines,  and  scattered  bristles  on  the 
dorsum. 

The  male  (fig.  56)  which  is  from  200- 
24oiAin  length,  and  150-200^  in  breadth, 
possesses  pedunculated  suckers  on  each 

pair  of  legs   except  the  third,  which  bears,  instead,  a  long  bristle. 

The  female  (fig.  56)  300-450^  in  length  and  2  5o-350[x  in  breadth,  has 

the  pedunculated  suckers  on  the  first  and  second  pairs  of  legs,  only, 

the  third  and  fourth  terminating  in  bristles. 
The  mite  lives  in  irregular  galleries  from 

a  few  millimeters  to  several  centimeters  in 

length,  which  it  excavates  in  the  epidermis 

(fig.    57).      It  works  especially  where  the 

skin  is  thin,  such  as  between   the  fingers, 

in  the  bend  of  the  elbows  and  knees,  and 

in  the  groin ,  but  it  is  by  no  means  restricted 

to  these  localities.       The  female,   alone, 

tiumels  into  the  skin;     the  males  remain 

under  the  superficial  epidermal  scales,  and 

seldom  are  found,  as  they  die  soon  after 

mating. 

As  she  burrows  into  the  skin  the  female 

deposits   her  eggs,  which  measure  about 

150  X  ioo[jL.     Fiirstenberg  says  thdt  each 

deposits   an   average  of    twenty-two    to  twenty-four  eggs,   though 

Gudden  reports  a  single  burrow  as  containing  fifty-one.     From  these 


566. 


Saicoptes  scabiei,  female. 
(X  ino.)  After  Fursten- 
berg. 


74 


Parasitic  Arthropods 


there  develop  after  about  seven  days,  the  hexapod  larvae.  These 
molt  on  the  sixteenth  day  to  form  an  octopod  nymph,  which  molts 
again  the  twenty-first  day.  At  the  end  of  the  fourth  week  the 
nymphs  molt  to  form  the  sexually  mature  males  and  the  so-called 
pubescent  females.  These  pair,  the  males  die,  and  the  females  again 
cast  their  skin,  and  become  the  oviparous  females.  Thus  the  life 
cycle  is  completed  in  about  twenty-eight  days. 

The  external  temperature  exercises  a  great  influence  on  the  develop- 
ment of  the  mites  and  thus,  during  the  winter,  the  areas  of  infesta- 
tion not  only  do  not  spread,  but  they  become  restricted.  As  soon  as 
the  temperature  rises,  the  mites  increase  and  the  infestation  becomes 
much  more  extensive. 


57.     Sarcoptes  scabiei.     Diagrammatic  representation  of  the  course  in 
the  skin  of  man. 


In  considering  the  possible  sources  of  infestation,  and  the  chances- 
of  reinfestation  after  treatment,  the  question  of  the  ability  of  the  mite 
to  live  apart  from  its  host  is  a  very  important  one.  Unfortunately,, 
there  are  few  reliable  data  on  this  subject.  Gerlach  found  that,, 
exposed  in  the  dry,  warm  air  of  a  room  they  became  very  inactive 
within  twenty -four  hours,  that  after  two  days  they  showed  only 
slight  movement,  and  that  after  three  or  four  days  they  could  not 
be  revived  by  moisture  and  warming.  The  important  fact  was 
brought  out  that  in  moist  air,  in  folded  soiled  underwear,  they  sur- 
vived as  long  as  ten  days.  Bourguignon  found  that  under  the  most 
favorable  conditions  the  mites  of  Sarcoptes  scabiei  equi  would  live  for 
sixteen    days. 

The  disease  designated  the  "itch"  or  "scabies,"  in  man  has  been 
known  from  time  immemorial,  but  until  within  less  than  a  hundred 
years  it  was  almost  universally  attributed  to  malnutrition,  errors  of 


Sarcoptidce,  or  Itch  Mites 


75 


diet,  or  "bad  blood."  This  was  in  spite  of  the  fact  that  the  mite  was 
known  to  Mouffet  and  that  Bonomo  had  figured  both  the  adult  and 
the  egg  and  had  declared  the  mite  the  sole  cause  of  the  disease.  In 
1834  the  Corsican  medical  student,  Francis  Renucci,  demonstrated 
the  mite  before  a  clinic  in  Saint  Louis  Hospital  in  Paris  and  soon 
thereafter  there  followed  detailed  studies  of  the  life  history  of  the 

various     itch    mites    of 
man  and  animals. 

The  disease  is  a  cos- 
mopolitan one,  being  ex- 
ceedingly abundant  in 
some  localities.  Its 
spread  is  much  favored 
where  large  numbers  of 
people  are  crowded  to- 
gether under  insanitary 
conditions  and  hence  it 
increases  greatly  during 
wars  and  is  widely  dis- 
seminated and  abundant 
immediately  afterwards. 
Though  more  commonly 
to  be  met  with  among 
the  lower  classes,  it  not 
infrequently  appears 
among  those  of  the  most 
cleanly,  careful  habits, 
and  it  is  such  cases  that 
are  most  liable  to  wrong 
diagnosis  by  the  physi- 
cian. 

Infection  occurs  solely  through  the  passage,  direct  or  indirect, 
of  the  young  fertilized  females  to  the  skin  of  a  healthy  individual. 
The  adult,  oviparous  females  do  not  quit  their  galleries  and  hence 
do  rot  serv^e  to  spread  the  disease.  The  young  females  move  about 
more  or  less  at  night  and  thus  the  principal  source  of  infestation  is 
through  sleeping  in  the  same  bed  with  an  infested  person,  or  indirectly 
through  bedclothes,  or  even  towels  or  clothing.  Diurnal  infestation 
through  contact  or  clothing  is  exceptional.  Many  cases  are  known 
of  the  disease  being  contracted  from  animals  suffering  from  scabies, 
or  mange. 


58.  Scpbies  on  the  hand.  From  portfoHo  of  Dermo- 
chromes  by  permission  of  Rebman  &  Co..  of 
New  York.  Publisheis. 


76 


Parasitic  Arthropods 


When  a  person  is  exposed  to  infestation,  the  trouble  manifests 
itself  after  eight  or  ten  days,  though  there  usually  elapses  a  period  of 

twenty  to  thirty  days  be- 
fore there  is  a  suspicion  of 
anything  serious.  The  first 
symptom  is  an  intense 
itching  which  increases 
when  the  patient  is  in  bed. 
When  the  point  of  irrita- 
tion is  examined  the  gal- 
leries may  usually  be  seen 
as  characteristic  sinuous 
lines,  at  first  whitish  in 
color  but  soon  becoming 
blackish  because  of  the  con- 
tained eggs  and  excrement. 
The  galleries,  which  may 
not  be  very  distinct  in 
some  cases,  may  measure 
as  much  as  four  centi- 
meters in  length.  Little 
vesicles,  of  the  size  of  a 
pin  head  are  produced  by 
the  secretions  of  the  feeding  mite ;  they  are  finn,  and  projecting,  and 
contain  a  limpid  fluid.  Figures  58 
and  59  show  the  typical  appearance 
of  scabies  on  the  hands,  while  figure 
60  shows  a  severe  general  infesta- 
tion .  The  intolerable  itching  induces 
scratching  and  through  this  various 
complications  may  arise .  The  lesions 
are  not  normally  found  on  the  face 
and  scalp,  and  are  rare  on  the  back. 
Formerly,  scabies  was  considered 
a  very  serious  disease,  for  its  cause 
and  method  of  treatment  were  un- 
known, and  potentially  it  may  con- 
tinue indefinitely.  Generation  after 
generation  of  the  mites  may  develop 

^   r       ^^       .  t      •  i  i  61).     Generalized  infection  of  Scabies 

and  finally  their  number  become  so  After  Morrow. 


59.     Scabies  on  the  hand.      After  Duhring. 


Sarcoptidcc,  or  Itch  Mites  77 

great  that  the  general  heahh  of  the  individual  is  seriously  affected. 
Now  that  the  true  cause  of  the  disease  is  known,  it  is  easily  con- 
trolled. 

Treatment  usually  consists  in  softening  the  skin  by  friction  with 
soap  and  warm  water,  followed  by  a  warm  bath,  and  then  appl^dng 
some  substance  to  kill  the  mites.  Stiles  gives  the  following  direc- 
tions, modified  from  Bourguignon's,  as  "a  rather  radical  guide,  to 
be  modified  according  to  facilities  and  according  to  the  delicacy  of  the 
skin  or  condition  of  the  patient" : 

I.  The  patient,  stripped  naked,  is  energetically  rubbed  all  over 
(except  the  head)  for  twenty  minutes,  with  green  soap  and  warm 
water.  2.  He  is  then  placed  in  a  warm  bath  for  thirty  minutes, 
during  which  time  the  rubbing  is  continued.  3.  The  parasiticide 
is  next  rubbed  in  for  twenty  minutes  and  is  allowed  to  remain  on  the 
body  for  four  or  fi^^e  hours ;  in  the  meantime  the  patient's  clothes  are 
sterilized,  to  kill  the  eggs  or  mites  attached  to  them.  4.  A  final 
bath  is  taken  to  remove  the  parasiticide. 

The  parasiticide  usually  relied  on  is  the  officinal  sulphur  ointment 
of  the  United  States  pharmacopoeia.  When  infestation  is  severe  it 
is  necessary  to  repeat  treatment  after  three  or  four  days  in  order 
to  kill  mites  which  have  hatched  from  the  eggs. 

The  above  treatment  is  too  severe  for  some  individuals  and  may, 
of  itself,  produce  a  troublesome  dermatitis.  We  have  seen  cases 
where  the  treatment  was  persisted  in  and  aggravated  the  condi- 
tion because  it  was  supposed  to  be  due  to  the  parasite.  For  deli- 
cate-skinned patients  the  use  of  balsam  of  Peru  is  very  satisfac- 
tory, and  usually  causes  no  irritation  whatever.  Of  course,  sources 
of  reinfection  should  be  carefully  guarded  against. 

Sarcoptes  scahiei  crustosce,  which  is  a  distinct  variety,  if  not  species, 
of  the  human  itch  mite,  is  the  cause  of  so-called  Norwegian  itch. 
This  disease  is  very  contagious,  and  is  much  more  resistant  than  the 
ordinary  scabies.  Unlike  the  latter,  it  may  occur  on  the  face  and 
scalp. 

Sarcoptes  scahiei  not  only  attacks  man  but  also  occurs  on  a  large 
number  of  mammals.  Many  species,  based  on  choice  of  host,  and 
minute  differences  in  size  and  secondary  characters,  have  been 
established,  but  most  students  of  the  subject  relegate  these  to 
varietal  rank.  Many  of  them  readily  attack  man,  but  they  have 
become  sufficiently  adapted  to  their  normal  host  so  that  they  are 
usually  less  persistent  on  man. 


78 


Parasitic  Arthropods 


Notoedres  cati  (usually  known  as  Sarcoptes  minor)  is  a  species 
of  itch  mites  which  produce  an  often  fatal  disease  of  cats.  The  body 
is  rounded  and  it  is  considerably  smaller  than  Sarcoptes  scabiei, 
the  female  (fig.  6i)  measuring  2I5-230[jl  long  and  165- i75[x  wide; 
the  males  i45-i50[jl  by   120-125^.     The  most  important  character 


61.     Notcedres  cati,  male  and  female.     After  Railliet. 

separating  Notoedres  from  Sarcoptes  is  the  position  of  the  anus, 
which  is  dorsal  instead  of  terminal.  The  mite  readily  transfers 
to  man  but  does  not  persist,  the  infestation  usually  disappearing 
MfrA  Spontaneously  in  about  two  weeks.     Infested  cats  are 

very  difhcult  to  cure,  unless  treatment  is  begun  at 
the  very  inception  of  the  outbreak,  and  under  ordi- 
nary circumstances  it  is  better  to  kill  them  promptly, 
to  avoid  spread  of  the  disease  to  children  and  others 
who  may  be  exposed. 

Demodecidae 

The  Demodecidae  are  small,  elongate,  vermiform 
mites  which  live  in  the  hair  follicles  of  mammals. 
The  family  characteristics  will  be  brought  out  in  the 
discussion  of  the  species  infesting  man,  Demodex 
folliculorum. 

Demodex  folliculorum  (fig.  62)  is  to  be  found  very 
commonly  in  the  hair  follicles  and  sebaceous  glands 
of  man.  It  is  vermiform  in  appearance,  and  with  the 
elongate  abdomen  transversely  striated  so  as  to  give 
62.  Demodex  foiii-  it  the  appearance  of  segmentation.  The  female  is  3  80- 
AftTmanSd.   4oo(x  long  by  45(J' ;  the  male  3oo[x  by  40[x.     The  three- 


DemodecidcB,  or  Hair-follicle  Mites 


79 


jointed  Ic^s,  eight  in  number,  are  reduced  to  mere  stubs  in  the  adult. 
The  larval  form  is  hcxopod.  These  mites  thus  show  in  their  form  a 
striking  adaptation  to  their  environment.     In  the  sebaceous  glands 


8  ■^ 


'v 


Mrazm  tii  ni>i  i-?  -•/  /M 


HudeX-    fclllCUlorUm      (Owen 


63.  D^modex  folliculorum.  Section  through  skin  showing  the 
mites  in  situ.  Magnification  of  Nos.  1,  2,  6  and  7,  X  150; 
Nos.  3.  4,  5,  X  450.     After  Megnin. 

and  hair  follicles  they  lie  with  their  heads  down  (fig.  63).  Usually 
there  are  only  a  few  in  a  gland,  but  Gruby  has  counted  as  many  as 
two  hundred. 

The  frequency  with  which  they  occur  in  man  is  surprising.  Ac- 
cording to  European  statistics  they  are  found  in  50  per  cent  to  60  per 
cent  or  even  more.     Gruby  found  them  in  forty  out  of  sixty  persons 


8o  Parasitic  Arthropods 

examined.  These  figures  are  very  commonly  quoted,  but  reliable 
data  for  the  United  States  seem  to  be  lacking.  Our  studies  indicate 
that  it  is  very  much  less  common  in  this  country'  than  is  generally 
assumed. 

The  Demodex,  in  man  docs  not,  as  a  rule,  cause  the  slightest 
inconvenience  to  its  host.  It  is  often  stated  that  they  give  rise  to 
comedons  or  "black-heads"  but  there  is  no  clear  evidence  that  they 
are  ever  implicated.  Certain  it  is  that  they  are  not  the  usual  cause. 
A  variety  of  the  same,  or  a  very  closely  related  species  of  Demodex, 
on  the  dog  gives  rise  to  the  very  resistant  and  often  fatal  follicular 
mange. 

Hexapoda   or   True   Insects 

The  Hexapoda,  or  true  insects,  arc  characterized  by  the  fact  that 
the  adult  i^ossesses  three  pairs  of  legs.  The  body  is  distinctly 
segmented  and  is  divided  into  head,  thorax,  and  abdomen. 

The  mouth-parts  in  a  generalized  form,  consist  of  an  upper  lip, 
or  labrum, \\-hich  is  a  part  of  the  head  capsule, and  a  central  unpaired 
hypopharynx,  two  mandibles,  two  maxillcB  and  a  lower  lip,  or  labium, 
made  up  of  the  fused  pair  of  second  maxilla?.  These  parts  may  be 
greatly  modified,  dependent  upon  whether  they  are  used  for  biting, 
sucking,  piercing  and  sucking,  or  a  combination  of  biting  and  sucking. 

Roughly  speaking,  insects  may  be  grouped  into  those  which 
undergo  complete  metamorphosis  and  those  which  have  incomplete 
metamorphosis.  They  are  said  to  undergo  complete  metamorphosis 
when  the  young  form,  as  it  leaves  the  egg,  bears  no  resemblance  to 
the  adult.  For  example,  the  maggot  changes  to  a  quiescent  pupa 
and  from  this  emerges  the  winged  active  fi}'.  They  undergo  incom- 
plete metamorphosis,  when  the  young  insect,  as  it  leaves  the  egg, 
resembles  the  adult  to  a  greater  or  less  extent,  and  after  under- 
going a  certain  number  of  molts  becomes  sexually  mature. 

Representatives  of  several  orders  have  been  reported  as  accidental 
or  faculative  parasites  of  man,  but  the  true  parasites  are  restricted 
to  four  orders.  These  arc  the  Siphunculata ;  the  Hemiptera,  the 
Diptera  and  the  Siphonaptera. 

Siphunculata 

The  order  Siphunculata  was  established  by  Meinert  to  include  the 
true  sucking  lice.  These  are  small  wingless  insects,  with  reduced 
mouth-parts,  adapted  for  sucking;  thorax  apparently  a  single  piece 
due  to  indistinct  separation  of  its  three  segments ;  the  compound  eyes 


Sipkunculata,  or  Lice 


8i 


64. 


Pediculus  showing  the  blind  sac  (6)  containing  the 
mouth  parts  (a)  beneath  the  alimentary  canal 
ip) .     After  Pawlowsky. 


reduced  to  a  single  ommatidium  on  each  side.  The  short,  powerful 
legs  are  terminated  by  a  single  long  claw.  Metamorphosis  incom- 
plete. 

There  has  been  a  great  deal  of  discussion  regarding  the  structure 
of  the  mouth-parts,  and  the  relationships  of  the  sucking  lice,  and  the 

questions  cannot  yet  be  re- 
garded as  settled.  The  con- 
flicting views  are  well  repre- 
sented by  Cholodkovsky 
(1904  and  1905)  and  by 
Enderlein  (1904). 

Following  Graber,  it  is 
generally  stated  that  the 
mouth-parts  consist  of  a 
short  tube  furnished  with 
hooks  in  front,  which  consti- 
tutes the  lower  lip,  and  that  within  this  is  a  delicate  sucking  tube 
derived  from  the  fusion  of  the  labrum  and  the  mandibles.  Opposed 
to  this,  CholodlcA^osky  and,  more  recently,  Pawlowsky,  (1906),  have 
shown  that  the  piercing  apparatus  lies  in  a  blind  sac  tmder  the 
pharynx  and  opening  into  the  mouth  cavity  (fig.  64).  It  does  not 
form  a  true  tube  but  a  furrow  with  its  open  surface  uppermost. 
Eysell  has  shown  that,  in  addition,  there  is  a  pair  of  chitinous  rods 
which  he  regards  as  the  homologues  of  the  maxillae. 

When  the  louse  feeds,  it  everts  the  anterior  part  of  the  mouth 
cavity,  with  its  circle  of  hooks.  The  latter  serve  for  anchoring 
the  bug,  and  the  piercing  apparatus  is  then  pushed 
out. 

Most  writers  have  classed  the  sucking  lice  as  a 
sub-order  of  the  Henliptera,  but  the  more  recent 
anatomical  and  developmental  studies  render  this 
grouping  untenable.  An  important  fact,  bearing  on 
the  question,  is  that,  as  shown  by  Gross,  (1905), 
the  structure  of  the  ovaries  is  radically  different 
from  that  of  the  Hemiptera. 

Lice  infestation  and  its  effects  are  known  medi- 
cally as  pediculosis.  Though  their  continued  pres- 
ence is  the  result  of  the  grossest  neglect  and  filthiness,  the  original 
infestation  may  be  innocently  obtained  and  by  people  of  the  most 
careful  habits.  ■ 


>.  Pediculushu- 
manus,  ventral  as- 
pect of  male.  (X  10) 


82 


Parasitic  Arthropods 


J 


Three  species  commonly  attack  man.  Strangely  enough,  there 
are  very  few  accurate  data  regarding  their  life  history. 

Pediculus  humanus  (fig.  65),  the  head  louse,  is  the  most  widely 
distributed.  It  is  usually  referred  to  in  medical  literature  as  Pedi- 
culus capitis,  but  the  Linnean  specific  name  has  priority.  In  color 
it  is  of  a  pale  gray,  blackish  on  the  margins.  It  is  claimed  by  some 
authors  that  the  color  varies  according  to  the  color  of  the  skin  of  the 

host.  The  abdomen  is 
composed  of  seven  dis- 
tinct segments,  bearing 
spiracles  laterally. 
There  is  considerable 
variation  in  size.  The 
males  average  1.8  mm. 
and  the  females  2 . 7  mm. 
in  length. 

The  eggs,  fift}'  to 
sixty  in  number,  stick 
firmly  to  the  hairs  of 
the  host  and  are  kno^vn 
as  nits.  They  are  large 
and  conspicuous,  especi- 
ally on  dark  hair  and 
are  provided  with  an 
operculum,  or  cap,  at 
the  free  end,  where  the 
nymphs  emerge.  They 
hatch  in  about  six  days 
and  about  the  eigh- 
teenth day  the  young 
lice  are  sexually  mature. 
The  head  lice  live  by  preference  on  the  scalp  of  their  host  but 
occasionalh^  they  are  found  on  the  eyelashes  and  beard,  or  in  the 
pubic  region.  They  may  also  occur  elsewhere  on  the  body  The 
penetration  of  the  rostrum  into  the  skin  and  the  discharge  of  an  irritat- 
ing saliva  produce  a  se\^ere  itching,  accompanied  by  the  formation 
of  an  eczema-like  eruption  (fig.  66).  When  the  infestation  is  severe, 
the  discharge  from  the  pustules  mats  down  the  hair,  and  scabs  are 
formed,  under  which  the  insects  swarm.  "  If  allowed  to  run,  a  regular 
carapace  may  form,  called  trichoma,  and  the  head  exudes  a  foetid 


V  -'itfftBf" 

■ 

¥ 

i 

\ 

66 


Pediculosis  of  the  head.  The  illustration  shows  the 
characteristic  indications  of  the  presence  of  lice,  viz: 
the  occipital  eczema  gluing  the  hairs  together,  the 
swollen  cervical  glands,  and  the  porrigo.  or  erup- 
tion of  contagious  pustules  upon  the  neck.  After 
Fo.x. 


Pediculus  Humanus  83 

odor.  Various  low  plants  may  grow  in  the  trichoma,  the  whole 
being  known  as  plica  palonica." — -Stiles. 

Sources  of  infestation  are  various.  School  children  may  obtain 
the  lice  from  seatmates,  by  wearing  the  hats  or  caps  of  infested  mates, 
or  by  the  use,  in  common,  of  brushes  and  combs.  They  may  be 
obtained  from  infested  beds  or  sleeper  berths.  Stiles  reports  an  in- 
stance in  which  a  large  number  of  girls  in  a  fashionable  boarding 
school  developed  lousiness  a  short  time  after  traveling  in  a  sleeijing 
car. 

Treatment  is  simple,  for  the  parasites  may  readily  be  controlled 
by  cleanliness  and  washing  the  head  with  a  two  per  cent  solution  of 
carbolic  acid  or  even  kerosene.  The  latter  is  better  used  mixed  with 
equal  parts  of  olive  oil,  to  avoid  irritation.  The  treatment  should 
be  applied  at  night  and  followed  the  next  morning  by  a  shampoo  with 
soap  and  warm  water.  It  is  necessary  to  repeat  the  operation  in  a 
few  days.  Xylol,  used  pure,  or  with  the  addition  of  five  per  cent 
of  vaseline,  is  also  very  efficacious.  Of  course,  the  patient  must  be 
cautioned  to  stay  away  from  a  lighted  lamp  or  fire  while  using  either 
the  kerosene  or  xylol.  While  these  treatments  will  kill  the  eggs  or 
nits,  they  will  not  remove  them  from  the  hairs.  Pusey  recommends 
repeated  washings  with  vinegar  or  25  per  cent  of  acetic  acid  in  water, 
for  the  purpose  of  loosening  and  removing  the  nits. 

Treatment  of  severe  infestations  in  females  is  often  troublesome 
on  account  of  long  hair.  For  such  cases  the  following  method  recom- 
mended by  Whitfield  (191 2)  is  especially  applicable: 

The  patient  is  laid  on  her  back  on  the  bed  with  her  head  over  the 
edge,  and  beneath  the  head  is  placed  a  basin  on  a  chair  so  that  the 
hair  lies  in  the  basin.  A  solution  of  i  in  40  carbolic  acid  is  then  poured 
over  the  hair  into  the  basin  and  sluiced  backwards  and  forwards 
imtil  the  whole  of  the  hair  is  thoroughly  soaked  with  it.  It  is  especi- 
ally necessary  that  care  should  be  taken  to  secure  thorough  satura- 
tion of  the  hair  over  the  ears  and  at  the  nape  of  the  neck,  since  these 
parts  are  not  only  the  sites  of  predilection  of  the  parasites  but  they 
are  apt  to  escape  the  solution.  This  sluicing  is  carried  out  for  ten 
minutes  by  the  clock.  At  the  end  of  ten  minutes  the  hair  is  lifted 
from  the  basin  and  allowed  to  drain,  but  is  not  dried  or  even  tho- 
roughly wrung  out.  The  whole  head  is  then  swathed  with  a  thick 
towel  or  better,  a  large  piece  of  common  house  flannel,  which  is 
fastened  up  to  form  a  sort  of  turban,  and  is  allowed  to  remain  thus 
for  an  hour.     It  can  then  be  washed  or  simply  allowed  to  dry,  as  the 


84  Parasitic  Arthropods 

carbolic  quickly  disperses.  At  the  end  of  this  period  every  pedicu- 
lus  and  what  is  better,  every  ovum  is  dead  and  no  relapse  will  occur 
unless  there  is  exposure  to  fresh  contagion.  Whitfield  states  that 
there  seem  to  be  no  disadvantages  in  this  method,  which  he  has  used 
for  years.  He  has  never  seen  carboluria  result  from  it,  but  would 
advise  first  cutting  the  hair  of  children  under  five  years  of  age. 

Pediculus  corporis  ( =  P.  vestimenti)  the  body  louse,  is  larger  than 
the  preceding  species,  the  female  measuring  3.3  mm.,  and  the  male 
3  mm.  in  length.  The  color  is  a  dirty  white,  or  grayish.  P.  corporis 
has  been  regarded  by  some  authorities  as  merely  a  variety  of  P. 
humanus  but  Piaget  maintains  there  are  good  characters  separating 
the  two  species. 

The  body  louse  li^^es  in  the  folds  and  seams  of  the  clothing  of  its 
host,  passing  to  the  skin  only  when  it  wishes  to  feed.  Brumpt 
states  that  he  has  found  enormous  nimibers  of  them  in  the  collars 
of  glass-ware  or  grains  worn  b}^  certain  naked  tribes  in  Africa. 

Exact  data  regarding  the  life-history  of  this  species  have  been 
supplied,  in  part,  by  the  work  of  Warburton  (1910),  cited  by  Nuttall. 
He  found  that  Pediculus  corporis  lives  longer  than  P.  humanus  under 
adverse  conditions.  This  is  doubtless  due  to  its  living  habitually 
on  the  clothing,  whereas  humanus  lives  upon  the  head,  where  it  has 
more  frequent  opportunities  of  feeding.  He  reared  a  single  female 
upon  his  own  person,  keeping  the  louse  enclosed  in  a  cotton-plugged 
tube  with  a  particle  of  cloth  to  which  it  could  cling.  The  tube  was 
kept  next  to  his  body,  thus  simulating  the  natural  conditions  of 
warmth  and  moisture  under  which  the  lice  thrive.  The  specimen 
was  fed  twice  daily,  while  it  clung  to  the  cloth  upon  which  it  rested. 
Under  these  conditions  she  lived  for  one  month.  Copulation  com- 
menced five  days  after  the  female  had  hatched  and  was  repeated  a 
number  of  times,  sexual  union  lasting  for  hours.  The  female  laid 
one  hundred  and  twenty-four  eggs  within  twenty-five  days. 

The  eggs  hatched  after  eight  days,  under  favorable  conditions, 
such  as  those  under  which  the  female  was  kept.  They  did  not 
hatch  in  the  cold.  Eggs  kept  near  the  person  during  the  day  and 
hung  in  clothing  by  the  bedside  at  night,  during  the  winter,  in  a  cold 
room,  did  not  hatch  until  the  thirty-fifth  day.  When  the  nymphs 
emerge  from  the  eggs,  they  feed  at  once,  if  given  a  chance  to  do  so. 
They  are  prone  to  scatter  about  the  person  and  abandon  the  frag- 
ment of  cloth  to  which  the  adult  clings. 


Pediculus  Corporis 


85 


The  adult  stage  is  reached  on  the  eleventh  day,  after  three  molts, 
about  four  days  apart.  Adtdts  enter  into  copulation  about  the 
fifth  day  and  as  the  eggs  require  eight  days  for  development, 
the  total  cycle,  tmder  favorable  conditions,  is  about  twenty- 
four  days.  Warburton's  data  differ  considerably  from  those  com- 
monly quoted  and  serve  to  emphasize  the  necessity  for  detailed  studies 
of  some  of  the  commonest  of  parasitic  insects. 

Body  lice  are  voracious  feeders,  producing  by  their  bites  and  the 
irritating  saliva  which  they  inject,  rosy  elevations  and  papules  which 
become  covered  with  a  brownish 
crust.  The  intense  itching  pro- 
A'okes  scratching,  and  character- 
istic white  scars  (fig.  67)  sur- 
rotmded  by  brownish  pigment 
(fig.  68)  are  formed.  The  skin 
may  become  thickened  and  take 
on  a  bronze  tinge.  This  mela- 
noderma is  especially  marked 
in  the  region  between  the  shoul- 
ders but  it  may  become  genera- 
lized, a  prominent  characteristic 
of  "vagabond's  disease."  Ac- 
cording to  Dubre  and  Beille, 
this  melanoderma  is  due  to  a 
toxic  substance  secreted  by  the 
lice,  which  indirectly  provokes 
the  formation  of  pigment. 

Control  measures,  in  the  case 
of  the  body  louse,  consist  in 
boiling  or  steaming  the  clothes  or  in  some  cases,  sterilizing  by  dry  heat. 
The  dermatitis  may  be  relieved  by  the  use  of  zinc-oxide  ointment, 
to  which  Pusey  recommends  that  there  be  added,  on  account  of  their 
parasiticidal  properties,  sulphur  and  balsam  of  Peru,  equal  parts,  15 
/CO  30  grains  to  the  ounce. 

Phthirius  pubis  (=  P.  inguinalis) ,  the  pubic  louse,  or  so-called 
"crab  louse,"  differs  greatly  from  the  preceding  in  appearance.  It  is 
characterized  by  its  relatively  short  head  which  fits  into  a  broad 
depression  in  the  thorax.  The  latter  is  broad  and  flat  and  merges 
into  the  abdomen.  The  first  pair  of  legs  is  slender  and  terminated 
by  a  straight  claw.     The  second  and  third  pairs  of  legs  are  thicker 


67. 


Pediculosis  in  man  caused  by  the  body 
louse.     After  Morrow. 


86 


Parasitic  Arthropods 


Ni 


and  are  provided  with  powerful  claws  fitted  for  clinging  to  hairs. 

The  females  (fig.  69)  measure  1.5  to  2  mm.  in  length  by  1.5  mm.  in 

breadth.  The  male  averages  a 
little  over  half  as  large.  The  eggs, 
or  nits,  are  fixed  at  the  base  of  the 
hairs.  Only  a  few,  ten  to  fifteen 
are  deposited  by  a  single  female, 
and  they  hatch  in  about  a  week's 
time.  The  young  lice  mature  in 
two  weeks. 

The  pubic  louse  usually  infests 
the  hairs  of  the  pubis  and  the 
perineal  region.  It  may  pass  to 
the  arm  pits  or  even  to  the  beard 
or  moustache.  Rarely,  it  occurs 
on  the  eyelids,  and  it  has  even 
been  found,  in  a  very  few  instances, 
occurring  in  all  stages,  on  the  scalp. 
Infestation  may  be  contracted 
from  beds  or  even  from  badh'  in- 
fested persons  in  a  crowd.  We 
have  seen  several  cases  which  un- 
doubtedly were  due  to  the  use  of 
public  water  closets.  It  produces 
papular  eruption  and  an  intense 
pruritis.  When  abundant,  there 
occurs  a  grayish  discoloration  of 
the  skin  which  Duguet  has  shown 


Melanoderma  caused  by  the  body 
louse.  From  Portfolio  of  Dermo- 
chromes,  by  permission  of  Rebman 
&  Co.,  New  York,  Publishers. 


is  due  to  ^  poisonous  saliva  injected  by  the  louse, 
as  is  the  melanoderma  caused  by  the  body  louse. 
The  pubic  louse  may  be  exterminated  by  the 
measures  recommended  for  the  head  louse,  or 
by  the  use  of  officinal  mercurial  ointment. 

Hemiptera 

Several  species  of  Hemiptera-Heteroptera  are 
habitual    parasites   of  man,   and    others   occur 
as  occasional  or   accidental   parasites.      Of  all 
these,  the  most  important  and  widespread  are  the  bed-bugs,  belong- 
ing to  the  genus  Cimex  (=  Acanthia). 


69. 


Phthirius  pubi?.  Ven- 
tral aspect  of  female. 
(X  12). 


The  Bed-bugs 


87 


The  Bed-bugs — The  bed-bugs  are  characterized  by  a  much  flat- 
tened oval  body,  with  the  short,  broad  head  unconstricted  behind, 
and  fitting  into  the  strongly  excavated  anterior  margin  of  the  thorax. 
The  compound  eyes  are  prominent,  simple  eyes  lacking.  Antennae 
four-jointed,  the  first  segment  short,  the  second  long  and  thick,  and 
the  third  and  fourth  slender.  The  tarsi  are  short  and  three  seg- 
mented. 

It  is  often  assumed  in  the  literature  of  the  subject  that  there  is 
but  a  single  species  of  Cimex  attacking  man,  but  several  such  species 
are  to  be  recognized.     These  are  distinguishable  by  the  characters 

given  in  Chapter  XII.  We  shall  con- 
sider especially  Cimex  lectularius,  the 
most  common  and  widespread  species. 
Cimex  lectularius  (=  Acanthia 
lectularia,  Clinocoris  lectularius),  is 
one  of  the  most  cosmopolitan  of  human 
parasites  but,  like  the  lice,  it  has  been 
comparatively  little  studied  until 
recent  years,  when  the  possibility 
that  it  may  be  concerned  with  the 
transmission  of  various  diseases  has 
awakened  interest  in  the  details  of 
its  life-history  and  habits. 

The  adult  insect  (fig.  70)  is  4-5 
mm.  long  by  3  mm.  broad,  reddish 
brown  in  color,  with  the  beak  and  body  appendages  lighter  in  color. 
The  short,  broad  and  somewhat  rectangular  head  has  no  neck-like 
constriction  but  fits  into  the  broadly  semilunar  prothorax.  The 
four  segmented  labiiun  or  proboscis  encloses  the  lancet-like  maxilla 
and  mandibles.  The  distal  of  the  four  antennal  segments  is  slightly 
club-shaped.  The  prothorax  is  characteristic  of  the  species,  being 
deeply  incised  anteriorly  and  with  its  thin  lateral  margins  somewhat 
turned  up.  The  mesothorax  is  triangular,  with  the  apex  posteriorly, 
and  bears  the  greatly  atrophied  first  pair  of  wings.  There  is  no  trace 
of  the  metathoracic  pair.  The  greatly  flattened  abdomen  has  eight 
visible  segments,  though  in  reality  the  first  is  greatly  reduced  and 
has  been  disregarded  by  most  writers.  The  body  is  densely  covered 
with  short  bristles  and  hairs,  the  former  being  peculiarly  saber- 
shaped  structures  sharply  toothed  at  the  apex  and  along  the  convex 
side  (fig.  1596). 


Cimex  lectularius  adult  and  eggs. 
Photograph  by  M.  V.  S. 


88  Parasitic  Arthropods 

The  peculiar  disagreeable  odor  of  the  adult  bed-bug  is  due  to  the 
secretion  of  the  stink  glands  which  lie  on  the  inner  surface  of  the 
mesostemum  and  open  by  a  pair  of  orifices  in  front  of  the  metacoxae, 
near  the  middle  line.  In  the  nymphs,  the  thoracic  glands  are  not 
developed  but  in  the  abdomen  there  are  to  be  found  three  unpaired 
dorsal  stink  glands,  which  persist  until  the  fifth  molt,  when  they 
become  atrophied  and  replaced  by  the  thoracic  glands.  The  nymphal 
glands  occupy  the  median  dorsal  portion  of  the  abdomen,  opening 
by  paired  pores  at  the  anterior  margin  of  the  fourth,  fifth  and  sixth 
segments.  The  secretion  is  a  clear,  oily,  volatile  fluid,  strongly  acid 
in  reaction.  Similar  glands  are  to  be  found  in  most  of  the  Hemiptera- 
Heteroptera  and  their  secretion  is  doubtless  protective,  through 
being  disagreeable  to  the  birds.  In  the  bed-bug,  as  Marlatt  points 
out,  "it  is  probably  an  illustration  of  a  very  common  phenomenon 
among  animals,  i.  e.,  the  persistence  of  a  characteristic  which  is  no 
longer  of  any  special  value  to  the  possessor."  In  fact,  its  possession 
is  a  distinct  disadvantage  to  the  bed-bug,  as  the  odor  frequently 
reveals  the  presence  of  the  bugs,  before  they  are  seen. 

The  eggs  of  the  bed-bug  (fig.  70)  are  pearly  white,  oval  in  out- 
line, about  a  millimeter  long-,  and  possess  a  small  operciilum  or  cap 
at  one  end,  which  is  pushed  off  when  the  young  hatches.  They  are 
laid  intermittently,  for  a  long  period,  in  cracks  and  crevices  of  beds 
and  furniture,  under  seams  of  mattresses,  under  loose  wall  paper, 
and  similar  places  of  concealment  of  the  adult  bugs.  Girault  (1905) 
observed  a  well-fed  female  deposit  one  hundred  and  eleven  eggs 
during  the  sixty-one  days  that  she  was  kept  in  captivity.  She  had 
apparently  deposited  some  of  her  eggs  before  being  captured. 

The  eggs  hatch  in  six  to  ten  days,  the  newly  emerged  nymphs 
being  about  1.5  mm.  in  length  and  of  a  pale  yellowish  white  color. 
They  grow  slowly,  molting  five  times.  At  the  last  molt  the  mesa- 
thoracic  wing  pads  appear,  characteristic  of  the  adult.  The  total 
length  of  the  nymphal  stage  varies  greatly,  depending  upon  condi- 
tions of  food  supply,  temperature  and  possibly  other  factors.  Mar- 
latt (1907)  found  under  most  favorable  conditions  a  period  averaging 
eight  days  between  molting  which,  added  to  an  equal  egg  period, 
gave  a  total  of  about  seven  weeks  from  egg  to  adult  insect.  Girault 
(19 1 2)  found  the  postembryonic  period  as  low  as  twenty-nine  days 
and  as  high  as  seventy  days  under  apparently  similar  and  normal 
conditions  of  food  supply.  Under  optimum  and  normal  conditions 
of  food  supply,  beginning  August  27,  the  average  nymphal  life  was 


The  Bed-bugs  89 

69.9  days;  average  number  of  meals  8.75  and  the  molts  5.  Under 
conditions  allowing  about  half  the  normal  food  supply  the  average 
nymphal  life  was  from  116.9  to  139  days.  Nymphs  starved  from 
birth  lived  up  to  42  days.  We  have  kept  unfed  nymphs,  of  the  first 
stage,  alive  in  a  bottle  for  75  days.  The  interesting  fact  was  brought 
out  that  under  these  conditions  of  minimum  food  supply  there  were 
sometimes  six  molts  instead  of  the  normal  number. 

The  adults  are  remarkable  for  their  longevity,  a  factor  which  is 
of  importance  in  considering  the  spread  of  the  insect  and  methods  of 
control.  Dufour  (1833)  (not  De  Geer,  as  often  stated)  kept  speci- 
mens for  a  year,  in  a  closed  vial,  without  food.  This  ability,  coupled 
with  their  ^villingness  to  feed  upon  mice,  bats,  and  other  small  mam- 
mals, and  even  upon  birds,  accounts  for  the  long  periods  that  deserted 
houses  and  camps  may  remain  infested.  There  is  no  evidence  that 
under  such  conditions  they  are  able  to  subsist  on  the  starch  of  the 
wall  paper,  juices  of  moistened  wood,  or  the  moisture  in  the  accumu- 
lations of  dust,  as  is  often  stated. 

There  are  three  or  four  generations  a  year,  as  Girault's  breeding 
experiments  have  conclusively  shown.  He  found  that  the  bed-bug 
does  not  hibernate  where  the  conditions  are  such  as  to  allow  it  to 
breed  and  that  breeding  is  continuous  unless  interrupted  by  the  lack 
of  food  or,  during  the  winter,  by  low  temperature. 

Bed-bugs  ordinarily  crawl  from  their  hiding  places  and  attack 
the  face  and  neck  or  uncovered  parts  of  the  legs  and  arms  of  their 
victims.  If  undisturbed,  they  will  feed  to  repletion.  We  have 
found  that  the  young  nymph  would  glut  itself  in  about  six  minutes, 
though  some  individuals  fed  continuously  for  nine  minutes,  while 
the  adult  required  ten  to  fifteen  minutes  for  a  full  meal.  When 
gorged,  it  quickly  retreats  to  a  crack  or  crevice  to  digest  its  meal, 
a  process  which  requires  two  or  three  days.  The  effect  of  the  bite 
depends  very  greatly  on  the  susceptibility  of  the  individual  attacked. 
Some  persons  are  so  little  affected  that  they  may  be  wholly  ignorant 
of  the  presence  of  a  large  number  of  bugs.  Usually  the  bite  produces 
a  small  hard  swelling,  or  wheal,  whitish  in  color.  It  may  even  be 
accompanied  by  an  edema  and  a  disagreeable  inflammation,  and  in 
such  susceptible  individuals  the  restlessness  and  loss  of  sleep  due  to 
the  presence  of  the  insects  may  be  a  matter  of  considerable  im- 
portance. Stiles  (1907)  records  the  case  of  a  young  man  who  under- 
went treatment  for  neurasthenia,  the  diagnosis  being  agreed  upon  by 
several  prominent  physicians;  ,all  symptoms  promptly  disappeared. 


go  Parasitic  Arthropods 

however,  immediately  following  a  thorough  fumigation  of  his  rooms, 
where  nearly  a  pint  of  bed-bugs  were  collected. 

It  is  natural  to  suppose  that  an  insect  which  throughout  its  whole 
life  is  in  such  intimate  relationship  with  man  should  play  an  important 
r61e  in  the  transmission  of  disease.  Yet  comparatively  little  is 
definitely  known  regarding  the  importance  of  the  bed-bug  in  this 
respect.  It  has  been  shown  that  it  is  capable  of  transmitting  the 
bubonic  plague,  and  South  American  trypanosomiasis.  Nuttall 
succeeded  in  transmitting  European  relapsing  fever  from  mouse  to 
mouse  by  its  bite.  It  has  been  claimed  that  Oriental  sore,  tubercu- 
losis, and  even  syphilis  may  be  so  carried.  These  phases  of  the 
subject  will  be  considered  later. 

The  sources  of  infestation  are  many,  and  the  invasion  of  a  house 
is  not  necessarily  due  to  neglect,  though  the  continued  presence  of 
the  pests  is  quite  another  matter.  In  apartments  and  closely  placed 
houses  they  are  known  to  invade  new  quarters  by  migration.  They 
are  frequently  to  be  met  with  in  boat  and  sleeper  berths,  and  even 
the  plush  seats  of  day  coaches,  whence  a  nucleus  may  be  carried  in 
baggage  to  residences.  They  may  be  brought  in  the  laundry  or 
in  clothes  of  servants. 

Usually  they  are  a  great  scourge  in  frontier  settlements  and  it  is 
generally  believed  that  they  live  in  nature  under  the  bark  of  trees, 
in  lumber,  and  under  similar  conditions.  This  belief  is  founded  upon 
the  common  occurrence  of  bugs  resembling  the  bed-bug,  in  such 
places.  As  a  matter  of  fact,  they  are  no  relation  to  bed-bugs  but 
belong  to  plant-feeding  forms  alone  (fig.  19  c,  d). 

It  is  also  often  stated  that  bed-bugs  live  in  poultry  houses,  in 
swallows  nests,  and  on  bats,  and  that  it  is  from  these  sources  that  they 
gain  access  to  dwellings.  These  bugs  are  specifically  distinct  from 
the  true  bed-bug,  but  any  of  them  may,  rarely,  invade  houses. 
Moreover,  chicken  houses  are  sometimes  thoroughly  infested  with 
the  true  Cimex  lectularius. 

Control  measures  consist  in  the  use  of  iron  bedsteads  and  the 
reduction  of  hiding  places  for  the  bugs.  If  the  infestation  is  slight 
they  may  be  exterminated  by  a  vigilant  and  systematic  hunt,  and 
by  squirting  gasoline  or  alcohol  into  cracks  and  crevices  of  the  beds, 
and  furniture.  Fumigation  must  be  resorted  to  in  more  general 
infestations. 

The  simplest  and  safest  method  of  fumigation  is  by  the  use  of 
flowers  of  sulphur  at  the  rate  of  two  pounds  to  each  one  thousand 


The  Bed-bugs  pi 

cubic  feet  of  room  space.  The  sulphur  should  be  placed  in  a  pan, 
a  well  made  in  the  top  of  the  pile  and  a  little  alcohol  poured  in,  to 
facilitate  burning.  The  whole  should  be  placed  in  a  larger  pan 
and  surrounded  by  water  so  as  to  avoid  all  danger  of  fire.  Windows 
should  be  tightly  closed,  beds,  closets  and  drawers  opened,  and 
bedding  spread  out  over  chairs  in  order  to  expose  them  fully  to  the 
fumes.  As  metal  is  tarnished  by  the  sulphur  fumes,  ornaments, 
clocks,  instruments,  and  the  like  should  be  removed.  When  all  is 
ready  the  sulphur  should  be  fired,  the  room  tightly  closed  and  left 
for  twelve  to  twenty-four  hours.  Still  more  efficient  in  large  houses, 
or  where  many  hiding  places  favor  the  bugs,  is  fumigation  with 
hydrocyanic  acid  gas.  This  is  a  deadly  poison  and  must  be  used 
under  rigid  precautions.  Through  the  courtesy  of  Professor  Herrick, 
who  has  had  much  experience  with  this  method,  we  give  in  the  Ap- 
pendix, the  clear  and  detailed  directions  taken  from  his  bulletin  on 
"Household  Insects." 

Fumigation  with  formaldehyde  gas,  either  from  the  liquid  or 
"solid"  formalin,  so  efficient  in  the  case  of  contagious  diseases,  is 
useless  against  bed-bugs  and  most  other  insects. 

Other  Bed-bugs — Cimex  hemipterus  (=  C.  rotundatus)  is  a  trop- 
ical and  subtropical  species,  occurring  in  both  the  old  and  new  world. 
Patton  and  Cragg  state  that  it  is  distributed  throughout  India, 
Burma,  Assam,  the  Malay  Peninsula,  Aden,  the  Island  of  Mauri- 
tius, Reunion,  St.  Vincent  and  Porto  Rico.  "It  is  widely  distribu- 
ted in  Africa,  and  is  probably  the  common  species  associated  there 
with  man."  Brumpt  also  records  it  for  Cuba,  the  Antilles,  Brazil, 
and  Venezuela. 

This  species,  which  is  sometimes  called  the  Indian  bed-bug, 
differs  from  C.  lectularius  in  being  darker  and  in  having  a  more 
elongate  abdomen.  The  head  also  is  shorter  and  narrower,  and  the 
prothorax  has  rounded  borders. 

It  has  the  same  habits  and  practically  the  same  life  cycle  as 
Cimex  lectularius.  Mackie,  in  India,  has  found  that  it  is  capable 
of  transmitting  the  Asiatic  type  of  recurrent  fever.  Roger  suggested 
that  it  was  also  capable  of  transmitting  kala-azar  and  Patton  has 
described  in  detail  the  developmental  stages  of  Leishmania,  the 
causative  organism  of  Kala-azar,  in  the  stomach  of  this  bug,  but 
Brumpt  declares  that  the  forms  described  are  those  of  a  common, 
non-pathogenic  flagellate  to  be  found  in  the  bug,  and  have  nothing 


92 


Parasitic  Arthropoda 


71.  Conorhinus 
sanguisugus. 


to  do  with  the  human  disease.  Brumpt  has  shown  experimentally 
that  Cimex  hemipterus  may  transmit  Trypanosoma  cruzi  in  its  excre- 
ment. 

Cimex  boueii,  occurring  in  French  Guinea,  is  another  species 
attacking  man.  Its  habits  and  general  life  history  are  the  same  as 
for  the  above  species.  It  is  3  to  4.5  mm.  in  length, 
has  vestigial  elytra,  and  much  elongated  antennae  and 
legs.  The  extended  hind  legs  are  about  as  long  as  the 
body. 

Cimex  columharius,  a  widely  distributed  species  nor- 
mally living  in  poiiltry  houses  and  dovecotes,  C.inodorus, 
infesting  poiiltry  in  Mexico,  C.  hirundinis,  occurring  in 
the  nests  of  swallows  in  Europe  and  Oeciacus  vicarius 
(fig.  I  pi)  occurring  in  swallow's  nests  in  this  country, 
are  species  which  occasionally  infest  houses  and  attack 
man. 
Conorhinus  sanguisugus,  the  cone-nosed  bed-bug.  We  have  seen 
in  our  consideration  of  poisonous  insects,  that  various  species  of 
Reduviid  bugs  readily  attack  man.  Certain  of  these  are  nocturnal 
and  are  so  commonly  found  in  houses  that  they  have  gained  the 
name,  of  "big  bed-bugs."  The  most  noted  of  these,  in  the  United 
States,  is  Conorhinus  sangitisugus  (fig.  71),  which  is  widely  dis- 
tributed in  our  Southern  States. 

Like  its  near  relatives,  Conorhinus 
sangiusugus  is  carnivorous  in  habit  and 
feeds  upon  insects  as  well  as  upon 
mammalian  and  human  blood.  It  is 
reported  as  often  occurring  in  poultry 
houses  and  as  attacking  horses  in 
bams.  The  life  history  has  been 
worked  out  in  considerable  detail  by 
Marlatt ,  (1902),  from  whose  account  we 
extract  the  following. 

The  eggs  are  white,  changing  to 
yellow  and  pink  before  hatching.  The 
young  hatch  within  twenty  days 
and  there   are    four  nymphal   stages. 

In  all  these  stages  the  insect  is  active  and  predaceous,  the  mouth- 
parts  (fig.  72)  being  powerfully  developed.  The  eggs  are  normally 
deposited,  and  the  early  stages  are  undoubtedly  passed,  out  of  doors, 


72. 


Beak  of  Conorhinus  sanguisugus. 
After  Marlatt. 


Cone-nosed  Bugs  93 

the  food  of  the  immature  forms  being  other  insects.  Immature 
specimens  are  rarely  found  indoors.  It  winters  both  in  the  partly 
gro\vn  and  adult  stage,  often  under  the  bark  of  trees  or  in  any 
similar  protection,  and  only  in  its  nocturnal  spring  and  early 
summer  flights  does  it  attack  men.  Marlatt  states  that  this  insect 
seems  to  be  decidedly  on  the  increase  in  the  region  which  it  parti- 
cidarly  infests, — the  plains  region  from  Texas  northward  and  west- 
ward. In  California  a  closely  related  species  of  similar  habits  is 
known  locally  as  the  "monitor  bug." 

The  effect  of  the  bite  of  the  giant  bed-bug  on  man  is  often  very 
severe,  a  poisonous  saliva  apparently  being  injected  into  the  wound. 
We  have  discussed  this  phase  of  the  subject  more  fully  under  the 
head  of  poisonous  insects. 

Conorhinus  megistus  is  a  Brazilian  species  very  commonly  attack- 
ing man,  and  of  special  interest  since  Chagas  has  shown  that  it  is 
the  carrier  of  a  trypanosomiasis  of  man.  Its  habits  and  life  history 
have  been  studied  in  detail  by  Neiva,  (19 10). 

This  species  is  now  pre-eminently  a  household  insect,  depositing 
its  eggs  in  cracks  and  crevices  in  houses,  though  this  is  a  relatively 
recent  adaptation.  The  nymphs  emerge  in  from  twenty  to  forty 
days,  depending  upon  the  temperature.  There  are  five  nymphal 
stages,  and  as  in  the  case  of  true  bed-bugs,  the  duration  of  these  is 
ver>^  greath'  influenced  by  the  availability  of  food  and  by  tempera- 
tiure.  Neiva  reckons  the  entire  life  cycle,  from  egg  to  egg,  as  requir- 
ing a  minimum  of  three  hundred  and  twenty-four  days. 

The  nymphs  begin  to  suck  blood  in  three  to  five  days  after  hatch- 
ing. They  usually  feed  at  night  and  in  the  dark,  attacking  especially 
the  face  of  sleeping  individuals.  The  bite  occasions  but  little  pain. 
The  immature  insects  live  in  cracks  and  crevices  in  houses  and 
invade  the  beds  which  are  in  contact  with  walls,  but  the  adults  are 
active  flyers  and  attack  people  sleeping  in  hammocks.  The  males 
as  well  as  the  females  are  blood  suckers. 

Like  many  blood-sucking  forms,  Conorhinus  megistus  can  endure 
for  long  periods  without  food.  Neiva  received  a  female  specimen 
which  had  been  for  fifty-seven  days  alive  in  a  tightly  closed  box. 
They  rarely  feed  on  two  consecutive  days,  even  on  smaU  quantities 
of  blood,  and  were  never  seen  to  feed  on  three  consecutive  days. 

Methods  of  control  consist  in  screening  against  the  adult  bugs, 
and  the  elimination  of  crevices  and  such  hiding  places  of  the  nymphs. 
Where  the  infestation  is  considerable,  fumigation  with  sulphur  is 
ad\dsable. 


94  Parasitic  Arthropoda 

Parasitic  Diptera  or  Flies 

Of  the  Diptera  or  two-winged  flies,  many  species  occasionally 
attack  man.  Of  these,  a  few  are  outstanding  pests,  many  of  them 
may  also  serve  to  disseminate  disease,  a  phase  of  our  subject  which 
will  be  considered  later.  We  shall  now  consider  the  most  important 
of  the  group  from  the  viewpoint  of  their  direct  attacks  on  man. 

Psychodidae  or  Moth-Flies 

The  Psychodidae  or  Moth-flies,  include  a  few  species  which  attack 
man,  and  at  least  one  species,  Phlehotomus  papatasii,  is  known 
to  transmit  the  so-called  "three-day  fever"  of  man.  Another  species 
is  supposed  to  be  the  vector  of  Peruvian  verruga. 

The  family  is  made  up  of  small,  sometimes  very  small,  nematocer- 
ous  Diptera,  which-  are  densely  covered  with  hairs,  giving  them  a 
moth-like  appearance.  The  wings  are  relatively  large,  oval  or 
lanceolate  in  shape,  and  when  at  rest  are  held  in  a  sloping  manner 
over  the  abdomen,  or  are  held  horizontally  in  such  a  way  as  to  give 
the  insect  a  triangular  outline.  Not  only  is  the  moth-like  appearance 
characteristic,  but  the  venationof  the  wings  (fig.  1 63,  d)  is  very  peculiar 
and,  according  to  Comstock,  presents  an  extremely  generalized  form. 
All  of  the  longitudinal  veins  separate  near  the  base  of  the  wing 
except  veins  R2  and  R3  and  veins  Mi  and  M2.  Cross  veins  are 
wanting  in  most  cases. 

Comparatively  little  is  known  regarding  the  life-histor}"  and 
habits  of  the  Psychodidae,  but  one  genus,  Phlebotomus,  contains 
minute,  blood-sucking  species,  commonly  known  as  sand-flies.  The 
family  is  divided  into  two  subfamilies,  the  Psychodinae  and  the 
Phlebotominae.  The  second  of  these,  the  PhlebotominaB,  is  of 
interest  to  us. 

The  Phlebotominae — The  Phlebotominae  differ  from  the  Psychod- 
inae in  that  the  radical  sector  branches  well  out  into  the  wing  rather 
than  at  the  base  of  the  wing.  They  are  usually  less  hairy  than  the 
Psychodinae.  The  ovipositor  is  hidden  and  less  strongly  chitinized. 
The  species  attacking  man  belong  to  the  genus  Phlebotomus,  small 
forms  with  relatively  large,  hairy  wings  which  are  held  upright, 
and  with  elongate  proboscis.  The  mandibles  and  maxillae  are  ser- 
rated and  fitted  for  biting. 

According  to  Miss  Summers  (1913)  there  are  twenty -nine  known 
species  of  the  genus  Phlebotomus,   five  European,   eleven  Asiatic, 


Phlebotomus  Flies  95 

seven  African  and  six  American.  One  species  only,  Phlebotomus 
vexator,  has  been  reported  for  the  United  States.  This  was  described 
by  Coquillett,  (1907), from  species  taken  on Plummer's  Island,  Mary- 
land. It  measures  only  1.5  mm.  in  length.  As  it  is  very  probable 
that  this  species  is  much  more  widely  distributed,  and  that  other 
species  of  these  minute  flies  will  be  found  to  occur  in  our  fauna,  we 
quote  Coquillett's  description. 

Plilebotonms  vexator,  Coq. :  Yellow,  the  mesonotum  brown, 
hairs  chiefly  brown;  legs  in  certain  lights  appear  brown,  but  are 
covered  with  a  white  tomentum ;  wings  hyaline,  unmarked ;  the  first 
vein  (Ri)  terminates  opposite  one-fifth  of  the  length  of  the  first 
submarginal  cell  (cell  Ro) ;  this  cell  is  slightly  over  twice  as  long 
as  its  petiole;  terminal,  homy  portion  of  male  claspers  slender, 
bearing  many  long  hairs;  the  apex  terminated  by  two  curved  spines 
which  are  more  than  one-half  as  long  as  the  preceding  part,  and  just 
in  front  of  these  are  two  similar  spines,  while  near  the  middle  of  the 
length  of  this  portion  is  a  fifth  spine  similar  to  the  others.  Length 
1.5  mm. 

The  life-history  of  the  Phlebotomus  flies  has  been  best  worked  out 
for  the  European  Phlebotomus  papatasii  and  we  shall  briefly  sum- 
marize the  account  of  Doerr  and  Russ  (19 13)  based  primarily  on  work 
on  this  species.  The  European  Phlebotomus  flies  appear  at  the 
beginning  of  the  warm  season,  a  few  weeks  after  the  cessation  of  the 
hea\'y'  rains  and  storms  of  springtime.  They  gradually  become  more 
abundant  until  they  reach  their  first  maximum,  which  in  Italy  is  near 
the  end  of  July  (Grassi).  They  then  become  scarcer  but  reach  a 
second  maximum  in  September.  At  the  beginning  of  winter  they 
vanish  completely,  hibernating  individuals  not  being  found. 

After  fertihzation  there  is  a  period  of  eight  to  ten  days  before  ovi- 
position.  The  eggs  are  then  deposited,  the  majority  in  a  single  mass 
covered  by  a  slimy  secretion  from  the  sebaceous  glands.  The  larvae 
emerge  in  fourteen  to  twenty  days.  There  is  uncertainty  as  to  the 
length  of  larval  life,  specimens  kept  in  captivity  remaining  fifty  or 
more  days  without  transforming.  Growth  may  be  much  more  rapid 
in  nature.  The  larvte  do  not  live  in  fluid  media  but  in  moist  detritus 
in  dark  places.  Marett  believes  that  they  live  chiefly  on  the  excre- 
ment of  pill-bugs  (Oniscidse)  and  lizards.  Pupation  always  occurs 
during  the  night.  The  remnants  of  the  larval  skin  remain  attached 
to  the  last  two  segments  of  the  quiescent  pupa  and  serve  to  attach 
it  to  the  stone  on  which  it  lives.  The  pupal  stage  lasts  eleven  to 
sixteen  days,  the  adult  escaping  at  night. 


96  Parasitic  Arthropoda 

Only  the  females  suck  blood.  They  attack  not  only  man  but  all 
warm-blooded  animals  and,  according  to  recent  workers,  also  cold- 
blooded forms,  such  as  frogs,  lizards,  and  larvae.  Indeed,  Townsend 
(1914)  believes  that  there  is  an  intimate  relation  between  Phlebotomus 
and  lizards,  or  other  reptiles  the  world  over.  The  Phlebotomus 
passes  the  daylight  hours  within  the  darkened  recesses  of  the  loose 
stone  walls  and  piles  of  rock  in  order  to  escape  wdnd  and  strong  light. 
Lizards  inhabit  the  same  places,  and  the  flies,  always  ready  to  suck 
blood  in  the  absence  of  light  and  wind,  have  been  found  more  prone 
to  suck  reptilian  than  mammalian  blood. 

On  hot  summer  nights,  when  the  wind  is  not  stirring,  the  Phleboto- 
mus flies,  or  sand-flies,  as  they  are  popularly  called,  invade  houses  and 
sleeping  rooms  in  swarms  and  attack  the  inmates.  As  soon  as  light 
begins  to  break  the  flies  either  escape  to  the  breeding  places,  or  cool, 
dark  places  protected  from  the  wind,  or  a  part  of  them  remain  in  the 
rooms,  hiding  behind  pictures,  under  garments,  and  in  similar  places. 
Wherever  the  Phlebotomus  flies  occur  they  are  an  intolerable  nui- 
sance. On  account  of  their  small  size  they  can  easily  pass  through 
the  meshes  of  ordinary  screens  and  mosqtiito  curtains.  They  attack 
silently  and  inflict  a  very  painful,  stinging  bite,  followed  by  itching. 
The  ankles,  dorsum  of  the  feet,  wrists,  inner  elbow,  knee  joint  and 
similar  places  are  favorite  places  of  attack,  possibly  on  account  of 
their  more  delicate  skin. 

Special  interest  has  been  attracted  to  these  little  pests  in  recent 
years,  since  it  has  been  shown  that  they  transmit  the  European 
"pappatici  fever"  or  "three  day  fever."  More  recently  yet,  it 
appears  that  they  are  the  carriers  of  the  virus  of  the  Peruvian  *  *  ver- 
ruga."    This  phase  of  the  subject  will  be  discussed  later. 

Control  measures  have  not  been  worked  out.  As  Newstead  says, 
"In  consideration  of  the  facts  which  have  so  far  been  brought  to  light 
regarding  the  economy  of  Phlebotomus,  it  is  clearly  evident  that  the 
task  of  suppressing  these  insects  is  an  almost  insurmountable  one. 
Had  we  to  deal  with  insects  as  large  and  as  accessible  as  mosquitoes, 
the  adoption  of  prophylactic  measures  would  be  comparatively  easy, 
but  owing  to  the  extremely  minute  size  and  almost  flea-like  habits  of 
the  adult  insects,  and  the  enormous  area  over  which  the  breeding- 
places  may  occur,  we  are  faced  with  a  problem  which  is  most  difficult 
of  solution."  For  these  reasons,  Newstead  considers  that  the  only 
really  prophylactic  measures  which  can  at  present  be  taken,  are  those 
which  are  considered  as  precautionary  against  the  bites  of  the  insects. 


Culctd<B,  or  Mosquitoes  97 

Of  repellents,  he  cites  as  one  of  the  best  a  salve  composed  of  the 
following : 

01.  Anisi 3  grs. 

01.  Eucalypti 3  grs. 

01.  Terebenth 3  grs. 

Unq.  Acid  Borac. 

Of  sprays  he  recommends  as  the  least  objectionable  and  at  the 
same  time  one  of  the  most  effective,  formalin.  "The  dark  portions 
and  angles  of  sleeping  apartments  should  be  sprayed  with  a  one  per 
cent,  solution  of  this  substance  ever}^  da}^  during  the  season  in  which 
the  flies  are  prevalent.  A  fine  spraying  apparatus  is  necessary  for 
its  application  and  an  excessi^•e  amount  must  not  be  applied.  It  is 
considered  an  excellent  plan  also  to  spray  the  mosquito  curtains 
regularly  ever}'  day  towards  sunset ;  nets  thus  treated  are  claimed  to 
repel  the  attacks  of  these  insects."  This  effectiveness  of  formalin  is 
very  surprising  for,  as  we  have  seen,  it  is  almost  wholly  ineffective 
against  bed-bugs,  mosquitoes,  house  flies  and  other  insects,  where  it 
has  been  tried. 

A  measure  which  promises  to  be  very  effective,  where  it  can  be 
adopted,  is  the  use  of  electric  fans  so  placed  as  to  produce  a  current 
of  air  in  the  direction  of  the  windows  of  sleeping  apartments.  On 
account  of  the  inability  of -the  Phlebotomus  flies  to  mthstand  even 
slight  breezes,  it  seems  ver>^  probable  that  they  would  be  unable  to 
enter  a  room  so  protected. 

CulicidsB  or  Mosquitoes 

From  the  medical  vie^\^3oint,  probably  the  most  interesting  and 
important  of  the  blood-sucking  insects  are  the  mosquitoes.  Certainly 
this  is  true  of  temperate  zones,  such  as  those  of  the  United  States. 
The  result  is  that  no  other  group  of  insects  has  aroused  such  wide- 
spread interest,  or  has  been  subjected  to  more  detailed  study  than 
have  the  mosquitoes,  since  their  role  as  carriers  of  disease  was  made 
known.  There  is  an  enormous  literature  dealing  with  the  group,  but 
fortunately  for  the  general  student,  this  has  been  well  summarized 
by  a  number  of  workers.  The  most  important  and  helpful  of  the 
general  works  are  those  of  Howard  (1901),  Smith  (1904),  Blanchard 
(1905),  Mitchell  (1907),  and  especially  of  Howard,  Dyar,  and  Knab, 
whose  magnificent  monograph  is  still  in  course  of  publication. 


98  Parasitic  Arthropoda 

Aside  from  their  importance  as  carriers  of  disease,  mosquitoes  are 
notorious  as  pests  of  man,  and  the  earHer  literature  on  the  group  is 
largely  devoted  to  references  to  their  enoiTnous  numbers  and  their 
blood-thirstiness  in  certain  regions.  They  are  to  be  found  in  all 
parts  of  the  world,  from  the  equator  to  the  Arctic  and  Antarctic 
regions.  Linnaeus,  in  the  "Flora  Lapponica,"  according  to  Howard, 
Dyar  and  Knab,  "dwells  at  some  length  upon  the  great  abundance  of 
mosquitoes  in  Lapland  and  the  torments  they  inflicted  upon  man  and 
beast.  He  states  that  he  believes  that  nowhere  else  on  earth  are  they 
found  in  such  abundance  and  he  compares  their  numbers  to  the  dust 
of  the  earth.  Even  in  the  open,  you  cannot  draw  your  breath  without 
having  your  mouth  and  nostrils  filled  with  them;  and  ointments  of 
tar  and  cream  or  of  fish  grease  are  scarcely  sufficient  to  protect  even 
the  case-hardened  cuticle  of  the  Laplander  from  their  bite.  Even  in 
their  cabins,  the  natives  cannot  take  a  mouthful  of  food  or  lie  down 
to  sleep  unless  they  are  fumigated  almost  to  suffocation."  In  some 
parts  of  the  Northwestern  and  Southwestern  United  States  it  is 
necessary  to  protect  horses  working  in  the  fields  by  the  use  of  sheets  or 
burlaps,  against  the  ferocious  attacks  of  these  insects.  It  is  a  sur- 
prising fact  that  even  in  the  dry  deserts  of  the  western  United  States 
they  sometimes  occur  in  enormous  numbers. 

Until  comparatively  recent  years,  but  few  species  of  mosquitoes 
were  known  and  most  of  the  statements  regarding  their  life-history 
were  based  upon  the  classic  work  of  Reaumur  (1738)  on  the  biology 
of  the  rain  barrel  mosquito,  Culex  pipiens.  In  1896,  Dr.  Howard 
refers  to  twenty-one  species  in  the  United  States,  now  over  fifty  are 
known;  Giles,  in  1900,  gives  a  total  of  two  hundred  and  forty-two 
for  the  world  fauna,  now  over  seven  hundred  species  are  known. 
We  have  found  eighteen  species  at  Ithaca,  N.  Y. 

All  of  the  known  species  of  mosquitoes  are  aquatic  in  the  larval 
stage,  but  in  their  life-histories  and  habits  such  great  differences  occur 
that  we  now  know  that  it  is  not  possible  to  select  any  one  species  as 
typical  of  the  group.  For  our  present  pur[:)ose  we  shall  first  discuss 
the  general  characteristics  and  structure  of  mosquitoes,  and  shall 
then  give  the  life-history  of  a  common  species,  following  this  by  a 
brief  consideration  of  some  of  the  more  striking  departures  from  what 
have  been  supposed  to  be  the  typical  condition. 

The  Culicidae  are  slender,  nematocerous  Diptera  with  narrow  wings, 
antennae  plumose  in  the  males,  and  usually  with  the  proboscis  much 
longer  than  the  head,  slender,  firm  and  adapted  for  piercing  in  the 


CuUcidce,  or  Mosquitoes 


99 


Ctnttnna 


Thorojc 


female.  The  most  characteristic  feature  is  that  the  margins  of  the 
^vings  and,  in  most  cases,  the  wing  veins  possess  a  fringe  of  scale-Hke 
hairs.  These  may  also  cover  in  part,  or  entirely,  the  head,  thorax, 
abdomen  and  legs.     The  females,  only,  suck  blood. 

On  account  of  the  importance  of  the  group  in  this  country  and  the 
desirability  of  the  student  being  able  to  determine  material  in  various 
stages,  we  show  in  the  accompanying  figures  the  characters  most 
used  in  classification. 

The  larvas  (fig.  73)  are  elongate, 
with  the  head  and  thorax  sharply 
distinct.  The  larval  antennse  are 
prominent,  consisting  of  a  single 
cylindrical  and  sometimes  curved 
segment.  The  outer  third  is  often 
narrower  and  bears  at  its  base  a 
fan-shaped  tuft  of  hairs,  the  ar- 
rangement and  abundance  of  which 
is  of  systematic  importance.  About 
the  mouth  are  the  so-called  rotary 
mouth  brushes,  dense  masses  of 
long  hairs  borne  by  the  labrum 
and  having  the  function  of  sweep- 
ing food  into  the  mouth.  The 
form  and  arrangement  of  thoracic, 
abdominal,  and  anal  tufts  of  hair 
vary  in  different  species  and  present 
characteristics  of  value.  On  either 
side  of  the  eighth  abdominal  seg- 
ment is  a  patch  of  scales  varying 
greatly  in  arrangement  and  number  and  of  much  value  in  separating 
species.  Respiration  is  by  means  of  trachese  which  open  at  the  apex 
of  the  so-called  anal  siphon,  when  it  is  present.  In  addition,  there 
are  also  one  or  two  pairs  of  tracheal  gills  which  vary  much  in  appear- 
ance in  different  species.  On  the  ventral  side  of  the  anal  siphon  is  a 
double  row  of  flattened,  toothed  spines  whose  number  and  shape  are 
likewise  of  some  value  in  separating  species.  They  constitute  the 
comb  or  pecten. 

The  pupa  (fig.  139, b)  unlike  that  of  most  insects,  is  active,  though  it 
takes  no  food.  The  head  and  thorax  are  not  distinctly  separated,  but 
the  slender  flexible  abdomen  in  sharply  marked  off.     The  antennas, 


Yeritral  brush 
of  dth  seamen, 


LcderaJ,  comi 
of  8th  je^ment 

r:(Urtu2>& 


Culex  larva  showing  details  of  external 
structure. 


loo  Parasitic  Arthropoda 

mouth-parts,  legs,  and  wings  of  the  future  adult  are  now  external,  but 
enclosed  in  chitinous  cases.  On  the  upper  surface,  near  the  base  of 
the  wings  are  two  trumpets,  or  breathing  tubes,  for  the  pupal  spiracles 
are  towards  the  anterior  end  instead  of  at  the  caudal  end,  as  in  the 
larva.  At  the  tip  of  the  abdomen  is  a  pair  of  large  chitinous  swim- 
ming paddles. 

As  illustrative  of  the  life  cycle  of  a  mosquito  we  shall  discuss  the 
development  of  a  common  house  mosquito,  Culex  pipiens,  often 
referred  to  in  the  Northern  United  States  as  the  rain  barrel  mosquito. 
Its  life  cycle  is  often  given  as  typical  for  the  entire  group,  but,  as  we 
have  already  emphasized,  no  one  species  can  serve  this  purpose. 

The  adults  of  Culex  pipiens  hibernate  throughout  the  winter  in 
cellars,  buildings,  hollow  trees,  or  similar  dark  shelters.  Early  in 
the  spring  they  emerge  and  deposit  their  eggs  in  a  raft-like  mass. 
The  number  of  eggs  in  a  single  mass  is  in  the  neighborhood  of  two 
hundred,  recorded  counts  varying  considerably.  A  single  female 
may  deposit  several  masses  during  her  life  time.  The  duration  of 
the  egg  stage  is  dependent  upon  temperature.  In  the  warm  summer 
time  the  larvae  may  emerge  within  a  day.  The  larvae  undergo  four 
molts  and  under  optimum  conditions  may  transform  into  pupas  in 
about  a  week's  time.  Under  the  same  favorable  conditions,  the  pupal 
stage  may  be  completed  in  a  day's  time.  The  total  life  cycle  of  Culex 
pipiens,  under  optimum  conditions,  may  thus  be  completed  in  a  week 
to  ten  days.  This  period  may  be  considerably  extended  under  less 
favorable  conditions  of  temperature  and  food  supply. 

Culex  pipiens  breeds  continuously  throughout  the  summer, 
developing  in  rain  barrels,  horse  troughs,  tin  cans,  or  indeed,  in  any 
standing  water  about  houses,  which  lasts  for  a  week  or  more.  The 
catch  basins  of  sewers  furnish  an  abundant  supply  of  the  pests  under 
some  conditions.  Such  places,  the  tin  gutters  on  residences,  and  all 
possible  breeding  places  must  be  considered  in  attempts  to  extermi- 
nate this  species. 

Other  species  of  mosquitoes  may  exhibit  radical  departures  from 
Culex  pipiens  in  life-history  and  habits.  To  control  them  it  is  essen- 
tial that  the  biological  details  be  thoroughly  worked  out  for,  as 
Howard,  Dyar,  and  Knab  have  emphasized,  "much  useless  labor  and 
expense  can  be  avoided  by  an  accurate  knowledge  of  the  habits  of  the 
species."  For  a  critical  discussion  of  the  known  facts  the  reader  is 
referred  to  their  monograph.  We  shall  confine  ourselves  to  a  few 
illustrations. 


CuUcidcB,  or  Mosquitoes  loi 

The  majority  of  mosquitoes  in  temperate  climates  hibernate  in 
the  egg  stage,  hatching  in  the  spring  or  even  mild  winter  days  in  water 
from  melting  snow.  It  is  such  single-brooded  species  which  appear  in 
astounding  numbers  in  the  far  North.  Similarly,  in  dry  regions  the 
eggs  may  stand  thorough  dessication,  and  yet  hatch  out  with  great 
promptness  when  submerged  by  the  rains.  "Another  provision  to 
insure  the  species  against  destruction  in  such  a  case,  exists  in  the  fact 
*  *  *  that  not  all  the  eggs  hatch,  a  part  of  them  lying  over  until 
again  submerged  by  subsequent  rains."  In  temperate  North 
America,  a  few  species  pass  the  winter  in  the  larval  state.  An  inter- 
esting illustration  of  this  is  afforded  by  Wyeomia  smithii,  whose 
larvce  live  in  pitcher  plants  and  are  to  be  found  on  the  coldest  winter 
days  imbedded  in  the  solid  ice.  Late  in  the  spring,  the  adults  emerge 
and  produce  several  broods  during  the  summer. 

In  the  United  States,  one  of  the  most  important  facts  which  has 
been  brought  out  by  the  intensive  studies  of  recent  years  is  that  cer- 
tain species  are  migratory  and  that  they  can  travel  long  distances  and 
become  an  intolerable  pest  many  miles  from  their  breeding  places. 
This  was  forcibly  emphasized  in  Dr.  Smith's  work  in  New  Jersey, 
when  he  found  that  migratory  mosquitoes,  developing  in  the  salt 
marshes  along  the  coast,  are  the  dominant  species  largely  responsible 
for  the  fame  of  the  New  Jersey  mosquito.  The  species  concerned  are 
Aedes  sollicitans,  A.  cantator  and  A.  tceniorhynchus .  Dr.  Smith 
decided  that  the  first  of  these  might  migrate  at  least  forty  miles 
inland.  It  is  obvious  that  where  such  species  are  the  dominant  pest, 
local  control  measures  are  a  useless  waste  of  time  and  money.  Such 
migratory  habits  are  rare,  however,  and  it  is  probable  that  the 
majority  of  mosquitoes  do  not  fly  any  great  distance  from  their 
breeding  places. 

While  mosquitoes  are  thought  of  primarily  as  a  pest  of  man,  there 
are  many  species  which  have  never  been  known  to  feed  upon  human 
or  mammalian  blood,  no  matter  how  favorable  the  opportunity. 
According  to  Howard,  Dyar,  and  Knab,  this  is  true  of  Ctilex  territans, 
one  of  the  common  mosquitoes  in  the  summer  months  in  the  Northern 
United  States.  There  are  some  species,  probably  many,  in  which 
the  females,  like  the  males,  are  plant  feeders.  In  experimental  work, 
both  sexes  are  often  kept  alive  for  long  periods  by  feeding  them  upon 
ripe  banana,  dried  fig,  raisins,  and  the  like,  and  in  spite  of  sweeping 
assertions  that  mosquitoes  must  have  a  meal  of  blood  in  order  to 
stimtdate  the  ovaries  to  development,  some  of  the  common  blood- 


I02  Parasitic  Arthropoda 

sucking  species,  notably  Culex  pipiens,  have  been  bred  repeatedly 
without  opportunity  to  feed  upon  blood. 

The  effect  of  the  bite  varies  greatly  with  different  species  and 
depends  upon  the  susceptibility  of  the  individual  bitten.  Some 
persons  are  driven  almost  frantic  by  the  attacks  of  the  pests  when 
their  companions  seem  almost  unconscious  of  any  inconvenience. 
Usually,  irritation  and  some  degree  of  inflammation  appear  shortly 
following  the  bite.  Not  infrequently  a  hardened  wheal  or  even  a 
nodule  forms,  and  sometimes  scratching  leads  to  secondary  infection 
and  serious  results. 

The  source  of  the  poison  is  usually  supposed  to  be  the  salivary 
glands  of  the  insect.  As  we  have  already  pointed  out,  (p.  34), 
Macloskie  believed  that  one  lobe  of  the  gland,  on  each  side,  was 
specialized  for  forming  the  poison,  while  a  radically  different  view  is 
that  of  Schaudinn,  who  believed  that  the  irritation  is  due  to  the 
expelled  contents  of  the  oesophageal  diverticula,  which  contain  a 
gas  and  a  peculiar  type  of  fungi  or  bacteria.  In  numerous  attempts, 
Schaudinn  was  unable  to  produce  any  irritation  by  applying  the 
triturated  salivary  glands  to  a  wound,  but  obtained  the  tyjjical  result 
when  he  used  the  isolated  diverticula. 

The  irritation  of  the  bite  may  be  relieved  to  some  extent  by  using 
ammonia  water,  a  one  per  cent,  alcoholic  solution  of  menthol,  or 
preparations  of  cresol,  or  carbolic  acid.  Dr.  Howard  recommends 
rubbing  the  bite  gently  with  a  piece  of  moist  toilet  soap.  Castellani 
and  Chalmers  recommend  cleansing  inflamed  bites  with  one  in  forty 
carbolic  lotion,  followed  by  dressing  with  boracic  ointment.  Of 
course,  scratching  should  be  avoided  as  much  as  possible. 

Repellents  of  various  kinds  are  used,  for  warding  off  the  attacks 
of  the  insects.  We  have  often  used  a  mixture  of  equal  parts  of  oil 
of  pennyroyal  and  kerosene,  applied  to  the  hands  and  face.  Oil  of 
citronella  is  much  used  and  is  less  objectionable  to  some  persons.  A 
recommended  formula  is,  oil  of  citronella  one  ounce,  spirits  of  camphor 
one  ounce,  oil  of  cedar  one-half  ounce.  A  last  resort  would  seem  to 
be  the  following  mixture  recommended  by  Howard,  Dyar,  and  Knab 
for  use  by  hunters  and  fishermen  in  badly  infested  regions,  against 
mosquitoes  and  blackflies. 

Take  2}i  lbs.  of  mutton  tallow  and  strain  it.  While  still  hot  add 
}4  lb.  black  tar  (Canadian  tar).  Stir  thoroughly  and  pour  into  the 
receptacle  in  which  it  is  to  be  contained.  When  nearly  cool  stir  in 
three  ounces  of  oil  of  citronella  and  i}i  oz.  of  pennyroyal. 


Culicidce,  or  Mosquitoes  103 

At  night  the  surest  protection  is  a  good  bed  net.  There  are  many 
types  of  these  in  use,  but  in  order  to  be  serviceable  and  at  the  same 
time  comfortable  it  should  be  roomy  and  hung  in  such  a  way  as  to 
be  stretched  tightly  in  every  direction.  We  prefer  one  suspended 
from  a  broad,  square  frame,  supported  by  a  right-angled  standard 
which  is  fastened  to  the  head  of  the  bed.  It  must  be  absolutely  free 
from  rents  or  holes  and  tucked  in  securely  under  the  mattress  or  it 
will  serve  merely  as  a  convenient  cage  to  retain  mosquitoes  which  gain 
an  entrance.  While  such  nets  are  a  convenience  in  any  mosquito 
riden  community,  they  are  essential  in  regions  where  disease-carrying 
species  abound.  Screening  of  doors,  windows  and  porches,  against 
the  pests  is  so  commonly  practiced  in  this  country  that  its  importance 
and  convenience  need  hardly  be  urged. 

Destruction  of  mosquitoes  and  prevention  of  breeding  are  of 
fundamental  importance.  Such  measures  demand  first,  as  we  have 
seen,  the  correct  determination  of  the  species  which  is  to  be  dealt 
with,  and  a  knowledge  of  its  life-history  and  habits.  If  it  prove  to  be 
one  of  the  migratory  forms,  it  is  beyond  mere  local  effort  and  becomes 
a  problem  demanding  careful  organization  and  state  control.  An 
excellent  illustration  of  the  importance  and  effectiveness  of  work 
along  these  lines  is  afforded  by  that  in  New  Jersey,  begun  by  the  late 
Dr.  John  B.  Smith  and  being  pushed  with  vigor  by  his  successor. 
Dr.  Headlee. 

In  any  case,  there  is  necessity  for  community  action.  Even  near 
the  coast,  where  the  migratory  species  are  dominant,  there  are  the 
local  species  which  demand  attention  and  which  cannot  be  reached 
by  any  measures  directed  against  the  species  of  the  salt  marshes.  The 
most  important  of  local  measures  consist  in  the  destruction  of  breed- 
ing places  by  filling  or  draining  ponds  and  pools,  clearing  up  of  more 
temporary  breeding  places,  such  as  cans,  pails,  water  barrels  and  the 
like.  Under  conditions  where  complete  drainage  of  swamps  is  im- 
practicable or  undesirable,  judicious  dredging  may  result  in  a  pool  or 
series  of  steep-sided  pools  deep  enough  to  maintain  a  supply  of  fish, 
which  will  keep  down  the  mosquito  larvae.  Where  water  receptacles 
are  needed  for  storage  of  rain  water,  they  should  be  protected  by 
careful  screening  or  a  film  of  kerosene  over  the  top  of  the  water, 
renewed  every  two  weeks  or  so,  so  as  to  prevent  mosquitoes  from 
depositing  their  eggs.  When  kerosene  is  used,  water  drawn  from  the 
bottom  of  the  receptacle  will  not  be  contaminated  by  it  to  any  in- 
jurious extent.     Where  ponds  cannot  be  drained  much  good  will  be 


I04 


Parasitic  Arthropoda 


accomplished  by  spraying  kerosene  oil  on  the  surface  of  the  water,  or 
by  the  introduction  of  fish  which  will  feed  on  the  larvae. 

Detailed  consideration  of  the 
most  efficient  measures  for  con- 
trolling mosquitoes  is  to  be  found 
in  Dr.  Howard's  Bulletin  No.  88 
of  the  Biireau  of  Entomolog}^ 
"Preventive  and  remedial  work 
against  mosquitoes"  or,  in  more 
summarized  form,  in  Farmers' 
Biilletin  No.  444.  One  of  these 
should  be  obtained  by  any  person 
interested  in  the  problems  of  mos- 
quito control  and  public  health. 


74.     Mouth  parts  of  Simulium.    After 
Griinberg. 


The  SimuliidaB,  or  Black  Flies 

The  Simuliidae,  or  black  flies,  are  small,  dark,  or  black  flies,  with 
a  stout  body  and  a  hump-back  appearance.  The 
antennae  are  short  but  eleven -segmented,  the  wings 
broad,  without  scales  or  hairs,  and  with  the  anterior 
veins  stout  but  the  others  very  weak.  The  mouth- 
parts  (fig.  74)  are  fitted  for  biting. 

The  larvce  of  the  Simuliidae  (fig.  75)  are  aquatic 
and,  unlike  those  of  mosquitoes,  require  a  well  aerated, 
or  swiftly  running  water.  Here  they  attach  to  stones, 
logs,  or  vegetation  and  feed  upon  various  micro- 
organisms. They  pupate  in  silken  cocoons  open  at 
the  top.  Detailed  life -histories  have  not  been  worked 
out  for  most  of  the  species.  We  shall  consider  as 
typical  that  of  Simulium  pictipes,  an  inoffensive 
species  widely  distributed  in  the  Eastern  United 
States,  which  has  been  studied  especially  at  Ithaca, 
N.Y.  (Johannsen,  1903). 

The  eggs  are  deposited  in  a  compact  yellowish  layer 
on  the  surface  of  rock,  on  the  brinks  of  falls  and 
rapids  where  the  water  is  flowing  swiftly.  They  are 
elongate  ellipsoidal  in  shape,  about  .4  by  .18  mm. 
As  myriads  of  females  deposit  in  the  same  place  the 
egg  patches  may  be  conspicuous  coatings  of  a  foot  or  much  more 
in  diameter.      When  first  laid  they  are  enveloped  in   a  yellowish 


75.    Larva  of  Simu- 
lium, (x8). 
After  Garman. 


Simuliid<2,  or  Black  Flies 


105 


white  slime,  which  becomes  darker,  until  finally  it  becomes  black  just 
before  the  emerging,'  of  the  larvae.     The  egg  stage  lasts  a  week. 

The  larvae  (fig.  75)  are  black,  soft  skinned,  somewhat  cylindrical 
in  shape,  enlarged  at  both  ends  and  attenuated  in  the  middle.  The 
posterior  half  is  much  stouter  than  the  anterior  part  and  almost  club- 
shaped.  The  head  bears  two  large  fan-shaped  organs  which  aid  in 
procuring  food.  Respiration  is  accomplished  by  means  of  three  so- 
called  blood  gills  which  are  pushed  out  from  the  dorsal  part  of  the 
Tectum.  The  lan'^ae  occur  in  enormous  numbers,  in  moss-like  patches. 
If  removed  from  their  natural  habitat  and  placed  in  quiet  water  they 
die  within  three  or  four  hours.  Fastened  to  the  rock  by  means  of  a 
disk-like  sucker  at  the  caudal  end  of 
the  body,  they  ordinarily  assume  an 
erect  position.  They  move  about  on 
the  surface  of  the  rocks,  to  a  limited 
extent,  ^^ath  a  looping  gait  similar  to 
that  of  a  measuring  worm,  and  a  web 
is  secreted  which  prevents  their  being 
washed  away  by  the  swiftly  fiomng 
water.  They  feed  chiefl}'  upon  algae 
and  diatoms. 

The  complete  lar\'al  stage  during 
the  summer  months  occupies  about 
four  weeks,  varying  somewhat  with  the 
temperature  and  velocity  of  the  water. 
At  the  end  of  this  period  they  spin 
from  cephalic  glands,  boot-shaped 
silken  cocoons  within  which  they  pupate.  The  cocoon  when  spun 
is  firmly  attached  to  the  rock  and  also  to  adjacent  cocoons. 
Clustered  continuously  over  a  large  area  and  sometimes  one  above 
another,  they  form  a  compact,  carpet-like  covering  on  the  rocks, 
the  reddish-browTi  color  of  which  is  easily  distinguishable  from  the 
jet-black  appearance  of  the  larvcc.  The  pupal  stage  lasts  about 
three  weeks.  The  adult  fly,  surrounded  by  a  bubble  of  air,  quickly 
rises  to  the  surface  of  the  water  and  escapes.  The  adults  (fig.  76) 
are  apparently  short  lived  and  thus  the  entire  life  cycle,  from  &gg 
to  egg  is  completed  in  approximately  eight  weeks. 

In  the  case  of  SimuUum  pictipes  at  Ithaca,  N.  Y.,  the  first  brood 
of  adults  emerges  early  in  May  and  successive  generations  are  produced 
throughout  the  summer  and  early  autum.n.     This  species  winters  in 


76.     Simulium  venustum,  (x8). 
After  Gamian. 


io6  Parasitic  Arthropoda 

the  larval  condition.  Most  of  the  other  species  of  Siniulium  which 
have  been  studied  seem  to  be  single  brooded. 

While  Siniulium  pictipes  does  not  attack  man,  there  are  a  number 
of  the  species  which  are  blood-sucking  and  in  some  regions  they  are  a. 
veritable  scourge.  In  recent  years  the  greatest  interest  in  the  group 
has  been  aroused  by  Sambon's  hypothesis  that  they  transmit  pellagra 
from  man  to  man.  This  has  not  been  established,  and,  indeed,  seems 
very  doubtful,  but  the  importance  of  these  insects  as  pests  and  the 
possibility  that  they  may  carr^^  disease  make  it  urgent  that  detailed 
life -histories  of  the  hominoxious  species  be  worked  out. 

As  pests  a  vivid  account  of  their  attacks  is  in  Agassiz's  "Lake 
Superior"  (p.  6i),  quoted  by  Forbes  (19 12). 

"Neither  the  love  of  the  picturesque,  however,  nor  the  interests  of 
science,  could  tempt  us  into  the  woods,  so  terrible  were  the  black  flies. 
This  pest  of  flies  which  all  the  way  hither  had  confined  our  ramblings 
on  shore  pretty  closely  to  the  rocks  and  the  beach,  and  had  been 
growing  constantly  worse,  here  reached  its  climax.  Although  de- 
tained nearly  two  days,  *  *  *  we  could  only  sit  with  folded 
hands,  or  employ  ourselves  in  arranging  specimens,  and  such  other 
operations  as  could  be  pursued  in  camp,  and  under  the  protection  of 
a  'smudge.'  One,  whom  scientific  ardor  tempted  a  little  way  up  the 
river  in  a  canoe,  after  water  plants,  came  back  a  frightful  spectacle, 
with  blood-red  rings  round  his  eyes,  his  face  bloody,  and  covered  with 
punctures.  The  next  morning  his  head  and  neck  were  swollen  as  if 
from  an  attack  of  er3^sipelas." 

There  are  even  well  authenticated  accounts  on  record  of  death  of 
humans  from  the  attacks  of  large  swarms  of  these  gnats.  In  some 
regions,  and  especially  in  the  Mississippi  Valley  in  this  countr>^  cer- 
tain species  of  black  flies  have  been  the  cause  of  enormous  losses  tO' 
farmers  and  stockmen,  through  their  attacks  on  poultry  and  domestic 
animals.  C.  V.  Riley  states  that  in  1874  the  loss  occasioned  in  one 
county  in  Tennessee  was  estimated  at  $500,000. 

The  measures  of  prevention  and  protection  against  these  insects 
have  been  well  summarized  b}'  Forbes  ( 1 9 1 2) .  The}^  are  of  two  kinds : 
"the  use  of  repellents  intended  to  drive  away  the  winged  flies,  and 
measures  for  the  local  destruction  of  the  aquatic  larvae.  The  repel- 
lents used  are  either  smudges,  or  surface  applications  made  to  keep 
the  flies  from  biting.  The  black-fly  wiU  not  endure  a  dense  smoke, 
and  the  well-known  mosquito  smudge  seems  to  be  ordinarily  sufficient 
for  the  protection  of  man.     In  the  South,  leather,  cloth,  and  other 


SimuliidcB,  or  Black  Flies  lof 

materials  which  will  make  the  densest  and  most  stifling  smoke,  are 
often  preserved  for  this  use  in  the  spring.  Smudges  are  built  in 
pastures  for  the  protection  of  stock,  and  are  kept  burning  before  the 
doors  of  bams  and  stables.  As  the  black-flies  do  not  readily  enter  a 
dark  room,  light  is  excluded  from  stables  as  much  as  possible  during 
the  gnat  season.  If  teams  must  be  used  in  the  open  field  while  gnats 
are  abroad,  they  may  be  protected  against  the  attacks  of  the  gnats  by 
applying  cotton-seed  oil  or  axle  grease  to  the  surface,  especially  to  the 
less  hairy  parts  of  the  animals,  at  least  twice  a  day.  A  mixture  of  oil 
and  tar  and,  indeed,  several  other  preventives,  are  of  practical  use  in 
badly  infested  regions;  but  no  definite  test  or  exact  comparison  has 
been  made  with  any  of  them  in  a  way  to  give  a  record  of  the  precise 
results." 

"It  is  easy  to  drive  the  flies  from  houses  or  tents  by  burning 
pyrethrum  powder  inside ;  this  either  kills  the  flies  or  stupifies  them 
so  that  they  do  not  bite  for  some  time  thereafter."  *  *  *  "Oil  of 
tar  is  commonly  applied  to  the  exposed  parts  of  the  body  for  the  pur- 
pose of  repelling  the  insects,  and  this  preparation  is  supplied  by  the 
Hudson  Bay  Company  to  its  employees.  Minnesota  fishermen 
frequently  grease  their  faces  and  hands  with  a  mixture  of  kerosene 
and  mutton  tallow  for  the  same  purpose."  We  have  found  a  mixture 
of  equal  parts  of  kerosene  and  oil  of  pennyroyal  efficient. 

Under  most  circumstances  very  little  can  be  done  to  destroy  this 
insect  in  its  early  stage,  but  occasionally  conditions  are  such  that  a 
larvicide  can  be  used  effectively.  Weed  (1904),  and  Sanderson  (19 10) 
both  report  excellent  results  from  the  use  of  phinotas  oil,  a  proprietary 
compound.  The  first -mentioned  also  found  that  in  some  places  the 
larvae  could  be  removed  by  sweeping  them  loose  in  masses  with  stiff 
stable  brooms  and  then  catching  them  downstream  on  wire  netting 
stretched  in  the  water. 

Chironomidae  or  Midges 

The  flies  of  this  family,  commonly  known  as  midges,  resemble 
mosquitoes  in  form  and  size  but  are  usually  more  delicate,  and  the 
wing- veins,  though  sometimes  hairy,  are  not  fringed  with  scales. 
The  venation  is  simpler  than  in  the  mosquitoes  and  the  veins  are 
usually  less  distinct. 

These  midges,  especially  in  spring  or  autumn,  are  often  seen  in 
immense  swarms  arising  like  smoke  over  swamps  and  producing  a 
humming  noise  which  can  be  heard  for  a  considerable  distance.     At 


io8 


Parasitic  A  rth  ropoda 


these  seasons  they  are  frequently  to  be  found  upon  the  windows  of 
dwelHngs,  where  they  are  often  mistaken  for  mosquitoes. 

The  larvae  are  worm-like,  but  vary  somewhat  in  form  in  the  differ- 
ent genera.  Most  of  them  are  aquatic,  but  a  few  live  in  the  earth,  in 
manure,  decaying  wood,  under  bark,  or  in  the  sap  of  trees,  especially 
in  the  sap  which  collects  in  wounds. 

Of  the  many  species  of  Chironomidae,  (over  eight  hundred  known) , 
the  vast  majority  are  inoffensive.  The  sub-family  Ceratopogoninae, 
however,  forms  an  exception,  for  some  of  the  members  of  this  group. 


77.      Culicoides  guttipennis;     (a)  adult,  (x  15);     {b)  head  of  same;     (c)  larva; 
{d)  head;    {e)  pupa.     After  Pratt. 


known  as  sandflies,  or  punkies,  suck  blood  and  are  particularly  trouble- 
some in  the  mountains,  along  streams,  and  at  the  seashore.  Most  of 
these  ha^^e  been  classed  tinder  the  genus  Ceratopogon,  but  the  group 
has  been  broken  up  into  a  number  of  genera  and  Ceratopogon,  in  the 
strict  sense,  is  not  known  to  contain  any  species  which  sucks  the  blood 
of  vertebrates.    • 

The  Ceratopogoninae — The  Ceratopogoninae  are  among  the  smallest 
of  the  Diptera,  many  of  them  being  hardly  a  millimeter  long  and  some 
not  even  so  large.  They  are  Chironomidae  in  which  the  thorax  is  not 
prolonged  over  the  head.  The  antennas  are  filiform  with  fourteen 
(rarely  thirteen)  segments  in  both  sexes,  those  of  the  male  being  brush- 
like.     The   basal  segment  is  enlarged,  the  last  segment  never  longer 


ChironomidoB ,  or  Midges 


109 


than  the  two  preceding  combined,  while  the  last  five  are  sub-equal  to, 
or  longer  than  the  preceding  segment.  The  legs  are  relatively  stouter 
than  in  the  other  Chironomidas.  The  follo\ving  three  genera  of  this 
subfamily  are  best  known  as  blood  suckers  in  this  country. 

Of  the  genus  Ciilicoides  there  are  many  species  occurring  in  various 
parts  of  the  world.  A  number  are  known  to  bite  man  and  animals  and 
it  is  probable  that  all  are  capable  of  inflicting  injury.  In  some 
localities  they  are  called  punkies,  in  others,  sand-flies,  a  name  some- 
times also  applied  to  the  species  of  Simulium  and  Phlebotomus. 
Owing  to  their  very  small  size  they  are  known  by  some  tribes  of 
Indians  as  No-see-tmis.  The  lar%^se  are  found  in  ponds,  pools,  water 
standing  in  hollow  tree  stumps,  and  the  like.  Though  probably  living 
chiefly  in  fresh  water,  we  have  found  a  species  occurring  in  salt  water. 
The  larvae  are  small,  slender,  legless, 
worm-hke  creatures  (fig.  77c)  with 
small  brown  head  and  twelve  body 
segments.  The  pupae  (fig.  77^)  are 
slender,  more  swollen  at  the  anterior 
end  and  terminating  in  a  forked  pro- 
cess. They  float  nearly  motionless  in 
a  vertical  position,  the  respiratory 
tubes  in  contact  with  the  surface  film. 
The  adults  are  all  small,  rarely  exceed- 
ing 2}4.  mm.  in  length.  The  wings 
are  more  or  less  covered  with  erect 
setulae  or  hairs  and  in  many  species 
variously    spotted   and   marked   with 

iridescent  blotches.  The  antennse  have  fourteen  segments,  the  palpi 
usually  five.  The  wing  venation  and  mouth-parts  are  shown  in 
figures  77  and  78.  Of  the  twenty  or  more  species  of  this  genus 
occurring  in  the  United  States  the  following  are  known  to  bite :  C. 
cinctus,  C.  guttipennis ,  C.  sanguisuga,  C.  stellifer,  C.  varnpennis, 
C.  unicolor. 

One  of  the  most  widely  distributed  and  commonest  species  in  the 
Eastern  States  is  C.  guttipennis  (fig.  77a).  It  is  black  with  brown 
legs,  a  whitish  ring  before  the  apex  of  each  femur  and  both  ends  of 
each  tibia;  tarsi  yellow,  knobs  of  halteres  yellow.  Mesonotum 
opaque,  brown,  two  vittae  in  the  middle,  enlarging  into  a  large  spot 
on  the  posterior  half,  also  a  curved  row  of  three  spots  in  front  of  each 
wing,  and  the  narrow  lateral  margins,  light  gray  pruinose.     Wings 


78. 


Culicoides   guttipennis;     mouth 
parts  of  adult.     After  Pratt. 


Pa  rasitic  A  rth  ropoda 


nearly  wholly  covered  with  brown  hairs,   gray,  with  markings  as 
shown  in  the  figure.     Length  one  mm. 

J ohannseniella  Will,  is  a 
wide-spread  genus  related 
to  the  foregoing.  Its 
mouth-parts  are  well 
adapted  for  piercing  and 
it  is  said  to  be  a  persistent 
blood  sucker,  partictdarly 
in  Greenland.  This  genus 
is  distinguished  from  Culi- 
coides  by  its  bare  wings, 
the  venation  (fig.  163,0), 
and  the  longer  tarsal  claws. 
There  are  over  twenty 
North  American  species. 
In  the  South\'\  estern  United  States,  Tersesthes  torrens  Towns, 
occurs,  a  little  gnat  which  annoys  horses,  and  perhaps  man  also,  by 
its  bite.  It  is  related  to  Culicoides  but  differs  in  the  number  of 
antennal  segments  and  in  its  wing  venation  (fig.  i63,e).  The  fly 
measures  but  two  mm.  in  length  and  is  blackish  in  color.  The 
antennae  of  the  female  have  thirteen  segments,  the  palpi  but  three,  of 
which  the  second  is  enlarged  and  swollen. 


79.     Chrysops  univittatus.  (X4).     After  Osborn 


Tabanidae  or  Horse-Flies 

The  Tabanidae, — horse-flies,  ear-flies,  and  deer-flies, — are  well- 
known  pests  of  cattle  and  horses  and  are  often  extremely  anno^dng 
to  man.  The  characteristics  of  the  family  and  of  the  principal  North 
American  genera  are  given  in  the  keys  of  Chapter  XII.  There  are 
over  2500  recorded  species.  As  in  the  mosquitoes,  the  females 
alone  are  blood  suckers.  The  males  are  flower  feeders  or  live  on 
plant  juices.  This  is  apparently  true  also  of  the  females  of  some  of 
the  genera. 

The  eggs  are  deposited  in  masses  on  water  plants  or  grasses  and 
sedges  growing  in  marshy  or  wet  ground.  Those  of  a  common 
species  of  Tahanus  are  illustrated  in  figure  80,  a.  They  are  placed 
in  masses  of  several  hundred,  light  colored  when  first  deposited  but 
turning  black.  In  a  week  or  so  the  cylindrical  larvae,  tapering  at 
both  ends  (fig.  80,  6),  escape  to  the  water,  or  damp  earth,  and  lead 


TabanidcB,  or  Horse-flies 


III 


an  active,  carnivorous  life,  feeding  mainly  on  insect  larvae,  and  worms. 
In  the  forms  which  have  been  best  studied  the  larval  life  is  a  long 

one,  lasting  for  months  or  even  for  more 

than  a  year.     Until  recently,  little  was 

known  concerning  the  life-histories  of  this 

group,  but  the  studies   of  Hart    (1895), 

and  Hine  (1903 

+  )  have  added 

greatly   to  the 

knowledge  con- 
cerning   North 

American 

forms. 

Many  of  the 

species     attack 

man  with  axad- 

ity  and  are  able 

to  inflict  painful 

bites,   which 

may  smart  for 

hours.    In  some 

instances    the 

wound     is     so 

considerable 

that  blood  wnW 

continue  to  flow 

after  the  fly  has 

left.     We  have 

seen    several 

cases   of    secondary    infection    following 

such  bites. 

The   horse-flies  have  been   definitely 

convicted  of  transferring  the  trypanosome 

of  surra  from  diseased  to  healthy  animals 
and  there  is  good  evidence  that  they  transfer  anthrax.  The  possi- 
bility of  their  being  important  agents  in  the  conveyal  of  human 
diseases  should  not  be  overlooked.  Indeed,  Leiper  has  recently 
determined  that  a  species  of  Chrysops  transfers  the  blood  parasite 
Filaria  diurna. 


so.     (6)  Larva  of  Tabanus. 
Photograph  by  M.  V.  S. 


80.     (a)  Eggs  of  Tabanus.     Photo 
graph  by  J.  T.  Lloyd. 


112 


LeptidcE,  or  Snipe -flies 


80.      (c)  Mouth  parts  of  Tabanus.   After  Griin 
berg. 


Leptidae  or  Snipe-Flies 

The  family  Leptidae  is  made  up  of  moderate  or  large  sized  flies, 
predaceous  in  habit.     They  are  sufficiently  characterized  in  the  keys 

of  Chapter  XII.  Four  blood- 
sucking species  belonging  to  three 
genera  have  been  reported.  Of 
these  Symphoromyia  pachyceras  is 
a  western  species.  Dr.  J.  C. 
Bradley,  from  personal  experience, 
reports  it  as  a  vicious  biter, 

Oestridae  or  Bot-flies 

To  the  family  Oestridae  belong 
the  bot  and  warble-flies  so  fre- 
quently injurious  to  animals. 
The  adtdts  are  large,  or  of 
medium  size,  heavy  bodied,  rather 
hairy,  and  usually  resemble  bees  in  appearance. 

The  larvse  live  parasitically  in  various  parts  of  the  body  of  mam- 
mals, such  as  the  stomach  (horse  bot-fly),  the  subcutaneous  con- 
nective tissue  (warble-fly  of  cattle),  or  the  nasal  passage  (sheep  bot- 
fly or  head  maggot) . 

There  are  on  record  many  cases  of  the  occurrence  of  the  larvae 
of  Oestridae  as  occasional  parasites  of  man.  A  number  of  these  have 
been  collected  and  re\'iewed  in  a  thesis  by  Mme.  Petrovskaia  (19 lo). 
The  majority  of  them  relate  to  the  following  species. 

Gastrophilus  hcemorrhoidalis ,  the  red  tailed  bot-fl^^  is  one  of  the 
species  whose  larvae  are  most  commonly  foimd  in  the  stomach  of  the 
horse.  Schoch  (1877)  cites  the  case  of  a  woman  who  suffered  from 
a  severe  case  of  chronic  catarrh  of  the  stomach,  and  who  vomited, 
and  also  passed  from  the  anus,  larva  which  apparently  belonged 
to  this  species.  Such  cases  are  exceedingly  rare  but  instances  of 
subcutaneous  infestation  are  fairly  numerous.  In  the  latter  type 
these  larvae  are  sometimes  the  cause  of  the  peculiar ' '  creeping  myasis. 
This  is  characterized  at  its  beginning  by  a  very  painful  swelling 
which  gradually  migrates,  producing  a  narrow  raised  line  four  to 
twenty-five  millimeters  broad.  When  the  larva  is  mature,  sometimes 
after  several  months,  it  becomes  stationary  and  a  tumor  is  formed 
which  opens  and  discharges  the  larva  along  with  pus  and  serum. 


PROPERTY  OF 

Z.  p.  METCALF 

OestridcB,  or  Bot-flies  113 

Gasiropkilus  equi  is  the  most  widespread  and  common  of  the  horse 
bot-flies.  Portschinsky  reports  it  as  commonly  causing  subcutan- 
eous myasis  of  man  in  Russia. 

Hypoderma  hovis  {  =  Oestrus  hovis),  and  Hypoderma  lineata  are 
the  so-called  warble-flies  of  cattle.  The  latter  species  is  the  more 
common  in  North  America  but  Dr.  C.  G.  Hewitt  has  recently  shown 
that  H.  hovis  also  occurs.  Though  warbles  are  very  common  in 
cattle  in  this  country,  the  adult  flies  are  very  rarely  seen.  They 
are  about  half  an  inch  in  length,  very  hairy,  dark,  and  closely  resemble 
common  honey-bees. 

They  deposit  their  eggs  on  the  hairs  of  cattle  and  the  animals  in 
licking  themselves  take  in  the  young  larvse.  These  pass  out  through 
the  walls  of  the  oesophagus  and  migrate  through  the  tissues  of  the 
animal,  to  finally  settle  down  in  the  subcutaneous  tissue  of  the  back. 
The  possibility  of  their  entering  directly  through  the  skin,  especially 
in  case  of  infestation  of  man,  is  not  absolutely  precluded,  although 
it  is  doubtful. 

For  both  species  of  Hypoderma  there  are  numerous  cases  on 
record  of  their  occurrence  in  man.  Hamilton  (1893)  saw  a  boy, 
six  years  of  age,  who  had  been  suffering  for  some  months  from  the 
glands  on  one  side  of  his  neck  being  swollen  and  from  a  fetid  ulcera- 
tion around  the  back  teeth  of  the  lower  jaw  of  the  same  side.  Three 
months'  treatment  was  of  no  avail  and  the  end  seemed  near;  one  day 
a  white  object,  which  was  seen  to  move,  was  observed  in  the  ulcer 
at  the  root  of  the  tongue,  and  on  being  extracted  was  recognized  as  a 
ftdl  grown  larva  of  Hypoderma.  It  was  of  usual  tawny  color,  about 
half  an  inch  long  when  contracted,  about  one  third  that  thickness, 
and  quite  lively.  The  case  resulted  fatally.  The  boy  had  been  on  a 
dairy  farm  the  previous  fall,  where  probably  the  egg  (or  larva)  was 
in  some  way  taken  into  his  mouth,  and  the  larva  found  between  the 
base  of  the  tongue  and  the  jaw  suitable  tissue  in  which  to  develop. 

Topsent  (1901)  reports  a  case  of  "creeping  myasis"  caused  by 
H.  lineata  in  the  skin  of  the  neck  and  shoulders  of  a  girl  eight  years 
of  age.  The  larva  travelled  a  distance  of  nearly  six  and  a  half  inches. 
The  little  patient  suffered  excruciating  pain  in  the  place  occupied  by 
the  larva. 

Hypoderma  diana  infests  deer,  and  has  been  known  to  occur  in 
man. 

Oestris  ovis,  the  sheep  bot-fly,  or  head  maggot,  is  widely  distrib- 
uted in  all  parts  of  the  world.     In    mid-summer  the   flies  deposit 


114  Parasitic  Arthropoda 

living  maggots  in  the  nostrils  of  sheep.  These  larvae  promptly  pass 
up  the  nasal  passages  into  the  frontal  and  maxillary  sinuses,  where 
they  feed  on  the  mucous  to  be  found  there.  In  their  migrations 
they  cause  great  irritation  to  their  host,  and  when  present  in  numbers 
may  cause  vertigo,  paroxysms,  and  even  death.  Portschinsky  in  an 
important  monograph  on  this  species,  has  discussed  in  detail  its 
relation  to  man.  He  shows  that  it  is  not  uncommon  for  the  fly  to 
attack  man  and  that  the  minute  living  larvae  are  deposited  in  the 
eyes,  nostrils,  lips,  or  mouth.  A  typical  case  in  which  the  larvae 
were  deposited  in  the  eye  was  described  by  a  German  oculist  Kayser, 
in  1905.  A  woman  brought  her  six  year  old  daughter  to  him  and 
said  that  the  day  before,  about  noontime,  a  flying  insect  struck  the 
eye  of'  the  child  and  that  since  then  she  had  felt  a  pain  which  in- 
creased towards  evening.  In  the  morning  the  pain  ceased  but  the 
eye  was  very  red.  She  was  examined  at  about  noon,  at  which  time 
she  was  quiet  and  felt  no  pain.  She  was  not  sensitive  to  light,  and 
the  only  thing  noticed  was  a  slight  congestion  and  accumulation  of 
secretion  in  the  comer  of  the  right  eye.  A  careful  examination  of 
the  eye  disclosed  small,  active,  white  larvae  that  crawled  out  from 
the  folds  of  the  conjunctiva  and  then  back  and  disappeared.  Five 
of  these  larvae  were  removed  and  although  an  uncomfortable  feeling 
persisted  for  a  while,  the  eye  became  normal  in  about  three  weeks. 

Some  of  the  other  recorded  cases  have  not  resulted  so  favorably, 
for  the  eyesight  has  been  seriously  affected  or  even  lost. 

According  to  Edmund  and  Etienne  Sergent  (1907),  myasis  caused 
by  the  larvae  of  Oestris  ovis  is  very  common  among  ^he  shepherds  in 
Algeria.  The  natives  say  that  the  fly  deposits  its  larvae  quickly, 
while  on  the  wing,  without  pause.  The  greatest  pain  is  caused  when 
these  larvas  establish  themselves  in  the  nasal  cavities.  They  then 
produce  severe  frontal  headaches,  making  sleep  impossible.  This 
is  accompanied  by  continuous  secretion  from  the  nasal  cavities 
and  itching  pains  in  the  sinuses.  If  the  larvse  happen  to  get  into 
the  mouth,  the  throat  becomes  inflamed,  swallowing  is  painful, 
and  sometimes  vomiting  results.  The  diseased  condition  may  last 
for  from  three  to  ten  days  or  in  the  case  of  nasal  infection,  longer, 
but  recovery  always  follows.  The  natives  remove  the  larvae  from 
the  eye  mechanically  by  means  of  a  small  rag.  When  the  nose  is 
infested,  tobacco  fumigations  are  applied,  and  in  case  of  throat 
infestation  gargles  of  pepper,  onion,  or  garlic  extracts  are  used. 


OestridcB,  or  Bot-flies 


115 


Larvae   of   Dermatobia   cyaniventris.     After    Blan- 
chard. 


RhincBstrus   nasalis,   the   Russian  gad-fly,   parasitizes    the    naso- 
pharyngeal region  of  the  horse.     According  to  Portschinsky,  it  not 

infrequently  attacks  man 
and  then,  in  all  the  known 
cases  deposits  its  larvae 
in  the  eye,  only.  This 
is  generally  done  while 
the  person  is  quiet,  but 
not  during  sleep.  The 
fly  strikes  without  stop- 
ping and  deposits  its  larva 
instantaneously.  Imme- 
diately after,  the  victim 
experiences  lancinating 
pains  which  without  in- 
termission increase  in 
violence.  '  There  is  an  in- 
tense conjunctivitis  and 
if  the  larvae  are  not  removed  promptly  the  envelopes 
ot  the  eye  are  gradually  destroyed  and  the  organ 
lost. 

Dermatobia  cyaniventris — This  fly  (fig.  83)  is  widely 
distributed  throughout  tropical  America,  and  in  its 
larval  stage  is  well  known  as  a  parasite  of  man.  The 
larvse  (figs.  81  and  82)  which  are  known  as  the  "ver 
macaque,"  "torcel,"  "ver  moyocuil"  or  by  several  other 
local  names,  enter  the  skin  and  give  rise  to  a  boil-like 
swelling,  open  at  the  top,  and  comparable  with  the  swell- 
ing produced  by  the  warble  fly  larvae,  in  cattle.  They 
cause  itching  and  occasional  excruciating  pain.  When 
mature,  nearly  an  inch  in  length,  they  voluntarily 
leave  their  host,  drop  to  the  ground  and  complete  their 
development.  The  adult  female  is  about  12  mm.  in 
length.  The  face  is  yellow,  the  frons  black  with  a 
grayish  bloom;  antennas  yellow,  the  third  segment 
four  times  as  long  as  the  second,  the  arista  pectinate. 
The  thorax  is  bluish  black  with  grayish  bloom;  the 
abdomen  depressed,  brilliant  metallescent  blue  with 
violet  tinge.  The  legs  are  yellowish,  the  squamae  and 
wings  brownish. 


82.  Young   larva  of 
Dermatobia  cy- 
aniventris. 
After  Surcouf. 


ii6 


Parasitic  Arthropoda 


S3.     Dermatobia  cyaniventris  (xlj^).     After  Graham-Smith. 


The  different  types  of  larvae  represented  in  figure  8 1  were  formerly- 
supposed  to  belong  to  different  species  but  Blanchard  regards  them 

as  merely  various  stages 
of  the  same  species.  It 
is  only  very  recently 
that  the  early  stage  and 
the  method  by  which 
man  becomes  infested 
were  made  known. 

About  1900,  Blanch- 
ard observed  the  pres- 
ence of  packets  of  large - 
sized  eggs  under  the 
abdomen  of  certain  mos- 
quitoes from  Central 
America;  and  in  19 10, 
Dr.  Morales,  of  Costa  Rica,  declared  that  the  Dermatobia  deposited 
its  eggs  directly  under  the  abdomen  of  the  mosquito  and  that  they 
were  thus  carried  to  vertebrates. 
Dr.  Nunez  Tovar  observed  the 
mosquito  carriers  of  the  eggs  and 
placing  larvae  from  this  source  on 
animals,  produced  typical  tumors 
and  reared  the  adult  flies.  It 
remained  for  Surcouf  (1913)  to 
work  out  the  full  details.  He 
found  that  the  Dermatobia  de- 
posits its  eggs  in  packets  covered 
by  a  very  viscid  substance,  on 
leaves.  These  become  attached 
to  mosquitoes  of  the  species 
Janthinosoma  lutzi  (fig.  84)  which 
walk  over  the  leaves.  The  eggs 
which  adhere  to  the  abdomen, 
remain  attached  and  are  thus 
transported.  The  embryo  de- 
velops, but  the  young  larva  (fig.  82)  remains  in  the  egg  until  it  has 
opportunity  to  drop  upon  a  vertebrate  fed  upon  by  the  mosquito. 


Mosquito  carrying   eggs   of   Dermatobia 
cyaniventris.     After  Surcouf. 


The  MuscidcB 


117 


Muscidse 

The  follo^^^ng  Muscidae,  characterized  elsewhere,  deserve  special 
mention  under  our  present  grouping  of  parasitic  species.     Other 
important  species  will  be  considered  as  facultative  para- 
sites. 

Stomoxys  calcitrans,  the  stable-fiy,  or  the  biting  house- 
fly, is  often  confused  ^vith  Musca  domestica  and  therefore 
is  discussed  especially  in  our  consideration  of  the  latter 
species  as  an  accidental  carrier  of  disease.  Its  possible 
relation  to  the  spread  of  infantile  paralysis  is  also  con- 
sidered later. 

The  tsetse  flies,   belonging  to  the  genus  Glossina,  are 
African  species  of  blood-sucking    Muscidae  which  have 
attracted  much  attention  because  of  their  role  in  trans- 
85   Larva  of  mitting  various  trypanosome  diseases  of  man  and  animals. 

Auchmero-  "  •'  ^ 

da'^Aftlr  'I^^y   ^^6    characterized   in    Chapter  XII   and  are  also 
Graham-  discusscd   in    conncction   with  the  diseases  which  they 

Smith.  •' 

convey. 

Chrysomyia  macellaria,  {  =  Compsomyia),  the  "screw  worm"-fly 
is  one  of  the  most  important  species  of  flies  directly  affecting  man, 
in  North  America.  It  is  not  normally  parasitic,  however,  and  hence 
will  be  considered  with  other  facultative  parasites  in  Chapter  IV. 

Auchmeromyia  lute- 
ola,  the  Congo  floor 
maggot.  This  is  a 
muscid  of  grewsome 
habits,  which  has  a  wide 
distribution  throughout 
Africa.  The  fly  (fig.  86) 
deposits  its  eggs  on  the 
ground  of  the  huts  of  the 
natives.  The  whitish 
larvae  (fig.  85)  on  hatch- 
ing are  slightly  flat- 
tened ventrally,  and 
each  segment  bears 
posteriorly  three  foot- 
pads transversely  arranged .  At  night  the  larvae  find  their  way  into  the 
low  beds  or  couches  of  the  natives  and  suck  their  blood.  The  adtilt 
flies  do  not  bite  man  and,  as  far  as  known,  the  larvae  do  not  play  any 
r61e  in  the  transmission  of  sleeping  sickness  or  other  diseases. 


Auchmeromyia  luteola  (x4).     After  Graham-Smith. 


ii8 


Parasitic  Arthropoda 


Cordylobia  anthropophaga  (x3). 
After  Fulleborn. 


This  habit  of  blood-sucking  by  muscid  larvae  is  usually  referred 
to  as  peculiar  to  Aucheromyia  luteola  but  it  should  be  noted  that  the 
__  larvae  of  Protocalliphora  frequent  the 

nests  of  birds  and  feed  upon  the 
young.  Mr.  A.  F.  Coutant  has  studied 
especially  the  life-history  and  habits 
of  P.  azurea,  whose  larvae  he  found 
attacking  young  crows  at  Ithaca ,  N .  Y. 
He  was  unable  to  induce  the  larvae  to 
feed  on  man. 

Cordylobia  anthropophaga,  {Ochro- 
myia  anthropophaga),  or  Tumbu-fly 
(fig.  87)  is  an  African  species  whose 
larvae  affect  man  much  as  do  those  of 
Dermatohia  cyniventris,  of  Central  and 
South  America.  The  larva  (fig.  88),  which  is  kno%vn  as  "ver  du 
Cayor"  because  it  was  first  observed  in  Cayor,  in  Senegambia, 
develops  in  the  skin  of  man  and  of  various  animals,  such  as  dogs, 
cats,  and  monkeys.  It  is  about  12  mm.  in  length,  and  of  the  form 
of  the  larvse  of  other  muscids.  Upon  the  intermediate  segments  are 
minute,  brownish  recurved  spines  which  give  to  the  larva  its  char- 
acteristic appearance.  The  life-history  is  not  satisfactorily  worked 
out,  but  Fuller  (19 14),  after  reviewing 
the  evidence  believes  that,  as  a  rule,  it 
deposits  its  young  in  the  sleeping  places 
of  man  and  animals,  whether  such  be  a 
bed,  a  board,  the  floor,  or  the  bare  ground. 
In  the  case  of  babies,  the  maggots  may 
be  deposited  on  the  scalp.  The  minute 
maggots  bore  their  way  painlessly  into 
the  skin.  As  many  as  forty  parasites 
have  been  found  in  one  individual  and 
one  author  has  reported  finding  more 
than  three  hundred  in  a  spaniel  puppy. 
Though  their  attacks  are  at  times  ex- 
tremely painful,  it  is   seldom   that  any     „„     ^         r  r^    ^  ,  ,,• 

-'     ^  -'88.      Larva  of   Cordylob;a  anthro- 

SerioUS  results  follow.  pophaga.     After  Blanchard. 


The  Siphonaptera  or  Fleas 
The  Siphonaptera   or   Fleas 


119 


The  Siphonaptera,  or  fleas  (fig.  89)  are  wingless  insects,  with 
highly  chitinized  and  laterally  compressed  bodies.  The  mouth-parts 
are  formed  for  piercing  and  sucking.  Compound  eyes  are  lacking 
but  some  species  possess  ocelli.     The  metamorphosis  is  complete. 

This  group  of  parasites,  concerning  which  little  was  known  until 
recenth',  has  assumed  a  very  great  importance  since  it  was  learned 


89.     Xenopsylla  cheopis,  male  (x25).     After  Jordan  and  Rothschild. 

that  fleas  are  the  carriers  of  bubonic  plague.  Now  over  four  hundred 
species  are  known.  Of  these,  several  species  commonly  attack  man. 
The  most  common  hominoxious  species  are  Pulex  irritans,  Xenopsylla 
cheopis,  Ctenocephalus  cams,  Ctenocephalus  felis,  Ceratophyllus 
fasciatus  and  Dermatophilus  penetrans,  but  many  others  will  feed 
readily  on  human  blood  if  occasion  arises. 

We  shall  treat  in  this  place  of  the  general  biology  and  habits  of 
the  hominoxious  forms  and  reserve  for  the  systematic  section  the 
discussion  of  the  characteristics  of  the  different  genera. 


I20 


Parasitic  Arthropoda 


90.     Dog  flea  (xlo).     After  Howard. 


The  most  common  fleas  infesting  houses  in  the  Eastern  United 
States  are  the  cosmopoHtan  dog  and  cat  fleas,  Ctenocephalus  canis 

(fig.  90)  and  C.  felis.  Their  life 
cycles  will  serve  as  typical. 
These  two  species  have  until 
recently  been  considered  as  one, 
under  the  name  Pulex  serraticeps. 
See  figure  92. 

The  eggs  are  oval,  slightly 
translucent  or  pearly  white,  and 
measure  about  .5  mm.  in  their 
long  diameter.  They  are  de- 
posited loosely  in  the  hairs  of 
the  host  and  readily  drop  off  as  the  animal  moves  around.  Howard 
found  that  these  eggs  hatch  in  one  to  two  days.  The  larvae  are 
elongate,  legless,  white,  worm-like  creatures.  They  are  exceed- 
ingly active,  and  avoid  the  light  in  every  way  possible.  They 
cast  their  first  skin  in  from  three  to  seven  days  and  their  second 
in  from  three  to  four  days.  They  commenced  spinning  in  from 
seven  to  fourteen  days  after  hatching  and  the  imago  appeared 
five  days  later.  Thus  in  summer,  at  Washington,  the  entire  life 
cycle  may  be  completed  in  about  two  weeks,     (cf.  fig.  91,  92). 

Strickland's  (19 14)  studies  on  the  biology  of  the  rat  flea,  Cerato- 
phyllus  fasciatus,  have  so  important  a  general  bearing  that  we  shall 
cite  them  in  considerable  detail. 

He  found,  to  begin  with,  that  there  is  a  marked  inherent  range 
in  the  rate  of  development.  Thus,  of  a  batch  of  seventy-three  eggs, 
all  laid  in  the  same  day  and  kept  together  under  the  same  condi- 


91.     Larva  of  Xenopsylla  cheopis.     After  Bacot  and  Ridewood. 

tions,  one  hatched  in  ten  days;  four  in  eleven  days;  twenty-five  in 
twelve  days ;  thirty-one  in  thirteen  days ;  ten  in  fourteen  days ;  one 
in  fifteen  days;  and  one  in  sixteen  days.  Within  these  limits  the 
duration  of  the  egg  period  seems  to  depend  mainly  on  the  degree 
of  humidity.     The  incubation  period  is  never  abnormally  prolonged 


Siphonaptera,  or  Fleas, 


121 


as  in  the  case  of  lice,  (Warburton)  and  varying  conditions  of  tempera- 
ture and  humidity  have  practically  no  effect  on  the  percentage  of 
eggs  which  ultimately  hatch. 

The  same  investigator  found  that  the  most  favorable  condition 
for  the  larv^a  is  a  low  temperature,  combined  with  a  high  degree  of 
humidity;  and  that  the  presence  of  rubbish  in  which  the  larv'-a  may 
bury  itself  is  essential  to  its  successftd  development.  When  larvee 
are  placed  in  a  bottle  containing  either  wood-wool  soiled  by  excre- 
ment, or  ^^dth  feathers  or  filter  paper  covered  with  dried  blood  they 


^lahia/  paJpu 


92.     Head  and  pronotum  of  (a)  dcg  flea;  (6)  of  cat  flea;  (c)  of  hen  flea.     After  Rothschild. 
(d)  Nycteridiphilus  (Ishnopsyllus)  hexactenus.     After  Oudemans. 

will  thrive  readily  and  pupate.  They  seem  to  have  no  choice  be- 
tween dried  blood  and  powdered  rat  feces  for  food,  and  also  feed 
readily  on  flea  excrement.     They  possess  the  curious  habit  of  always 

devouring  their  molted  skins. 

.    I  . 

An  important  part  of  Strickland's  experiments  dealt  wirth  the 

question  of  duration  of  the  pupal  stage  under  the  influence  of  tempera- 
ture and  \\4th  the  longevity  and  habits  of  the'  adult.  In  October, 
he  placed  a  batch  of  freshly  formed  cocoons  in  a  small  dish  that  was 
kept  near  a  white  rat  in  a  deep  glass  jar  in  the  laboratory.  Two 
months  later  one  small  and  feeble  flea  had  emerged,  but  no  more 
until  February,  four  months  after  the  beginning  of  the  experiment. 
Eight  cocoons  were  then  dissected  and  seven  more  found  to  contain 
the  imago  fully  formed  but  in  a  resting  state.     The  remainder  of 


122  Parasitic  Arthropoda 

the  batch  was  then  placed  at  70°  F.  for  one  night,  near  a  white 
rat.  The  next  day  all  the  cocoons  were  empty  and  the  fleas  were 
found  on  the  white  rat. 

Thus,  temperature  greatly  influences  the  duration  of  the  pupal 
period,  which  in  Ceratophyllus  fasciatus  averages  seventeen  days. 
Moreover,  when  metamorphosis  is  complete  a  low  temperature  will 
cause  the  imago  to  remain  within  the  cocoon. 

Sexually  mature  and  ovipositing  fleas,  he  fed  at  intervals  and  kept 
alive  for  tw^o  months,  when  the  experiment  was  discontinued.  In 
the  presence  of  rubbish  in  which  they  covdd  bury  themselves,  unfed 
rat  fleas  w^ere  kept  alive  for  many  months,  whereas  in  the  absence  of 
any  such  substratum  they  rarely  lived  a  month.  In  the  former  case, 
it  was  found  that  the  length  of  life  is  influenced  to  some  degree  by  the 
temperature  and  humidity.  In  an  experiment  carried  out  at  70°  F. 
and  45  per  cent  hiimidity,  the  fleas  did  not  live  for  more  than  four 
months,  while  in  an  experiment  at  60°  F.  and  70  per  cent  humidity 
they  lived  for  at  least  seventeen  months.  There  was  no  indication 
that  fleas  kept  under  these  conditions  sucked  moisture  from  surround- 
ing objects,  and  those  kept  in  bell  jars,  with  an  extract  of  flea-rubbish 
on  filter  paper,  did  not  li\^e  any  longer  than  those  which  were  not  so 
supplied. 

Curiously  enough,  although  the  rat  is  the  normal  host  of  Cerato- 
phyllus fasciatus,  it  was  found  that  when  given  the  choice  these  fleas 
would  feed  upon  man  in  preference  to  rats.  However,  none  of  the 
fleas  laid  eggs  unless  they  fed  on  rat  blood. 

The  experiments  of  Strickland  on  copulation  and  oviposition  in 
the  rat  flea  showed  that  fleas  do  not  copulate  until  they  are  sexually 
mature  and  that,  at  least  in  the  case  of  Ceratophylhis  fasciatus,  the 
reproductive  organs  are  imperfectly  developed  for  some  time  (more 
than  a  week)  after  emerging  from  the  pupa.  When  mature,  copula- 
tion takes  place  soon  after  the  fleas  have  fed  on  their  true  host — the 
rat — but  not  if  they  have  fed  on  a  facultative  host  only,  such  as  man. 
Copulation  is  always  followed  by  oviposition  within  a  very  short 
time. 

The  eftect  of  the  rat's  blood  on  the  female  with  regard  to  egg- 
laying,  Strickland  concludes,  is  stimulating  rather  than  nutritive, 
as  fleas  that  were  without  food  for  many  months  were  observed  tO' 
lay  eggs  immediately  after  one  feed.  Similarly,  the  male  requires 
the  stimulus  of  a  meal  of  rat's  blood  before  it  displays  any  copulatory 
activity. 


Siphonaptera,  or  Fleas  .  123 

Mitzmain  (1910)  has  described  in  detail  the  act  of  biting  on  man, 
as  observed  in  the  squirrel  flea,  Ceratophyllus  acutus.  "The  flea 
when  permitted  to  walk  freely  on  the  arm  selects  a  suitable  hairy 
space  where  it  ceases  abruptly  in  its  locomotion,  takes  a  firm  hold 
with  the  tarsi,  projects  its  proboscis,  and  prepares  to  puncture  the 
skin.  A  puncture  is  drilled  by  the  pricking  epipharynx,  the  saw- 
tooth mandibles  supplementing  the  movement  by  lacerating  the 
cavity  formed.  The  two  organs  of  the  rostrum  work  alternately, 
the  middle  piece  boring,  while  the  two  lateral  elements  execute  a 
sawing  movement.  The  mandibles,  owing  to  their  basal  attach- 
ments, are,  as  is  expressed  by  the  advisory  committee  on  plague 
investigations  in  India  (Journal  of  Hygiene,  vol.  6,  No.  4,  p.  499), 
'capable  of  independent  action,  sliding  up  and  down  but  maintaining 
their  relative  positions  and  preserving  the  lumen  of  the  aspiratory 
channel.'  The  labium  doubles  back,  the  V-shaped  groove  of  this 
organ  guiding  the  mandibles  on  either  side." 

"The  action  of  the  proboscis  is  executed  with  a  forward  movement 
of  the  head  and  a  lateral  and  downward  thrust  of  the  entire  body. 
As  the  mouth-parts  are  sharply  inserted,  the  abdomen  rises  simultane- 
ously. The  hind  and  middle  legs  are  elevated,  resembling  oars. 
The  forelegs  are  doubled  under  the  thorax,  the  tibia  and  tarsi  resting 
firmly  on  the  epidermis  serve  as  a  support  for  the  body  during  the 
feeding.  The  maxillary  palpi  are  retracted  beneath  the  head  and 
thorax.  The  labium  continues  to  bend,  at  first  acting  as  a  sheath 
for  the  sawing  mandibles,  and  as  these  are  more  deeply  inserted,  it 
bends  beneath  the  head  with  the  elasticity  of  a  bow,  forcing  the 
mandibles  into  the  wound  until  the  maxillse  are  embedded  in  the  skin 
of  the  victim.  When  the  proboscis  is  fully  inserted,  the  abdomen 
ceases  for  a  time  its  lateral  swinging." 

"The  acute  pain  of  biting  is  first  felt  when  the  mandibles  have 
not  quite  penetrated  and  subsequently  during  each  distinct  move- 
ment of  the  abdomen.  The  swinging  of  the  abdomen  gradually 
ceases  as  it  becomes  filled  with  blood.  The  sting  of  the  biting 
gradually  becomes  duller  and  less  sensitive  as  feeding  progresses. 
The  movements  of  the  elevated  abdomen  grow  noticeably  feebler 
as  the  downward  thrusts  of  the  springy  bow-like  labium  becomes  less 
frequent." 

"As  the  feeding  process  advances  one  can  discern  through  the 
translucent  walls  of  the  abdomen  a  constant  flow  of  blood,  caudally 
from  the  pharynx,  accompanied  by  a  peristaltic  movement.     The 


124  Parasitic  Arthropoda 

end  of  the  meal  is  signified  in  an  abrupt  manner.  The  flea  shakes 
its  entire  body,  and  gradually  withdraws  its  proboscis  by  lowering 
the  abdomen  and  legs  and  violently  twisting  the  head." 

"When  starv^ed  for  several  days  the  feeding  of  the  rat  fleas  is 
conducted  in  a  rather  vigorous  manner.  As  soon  as  the  proboscis 
is  buried  to  the  full  length  the  abdomen  is  raised  and  there  ensues  a 
gradual  lateral  swaying  motion,  increasing  the  altitude  of  the  raised 
end  of  the  abdomen  until  it  assumes  the  perpendicular.  The  flea  is 
obser\^ed  at  this  point  to  gain  a  better  foothold  b^^  advancing  the 
fore  tarsi,  and  then,  gradually  doubling  back  the  abdomen,  it  turns 
with  extreme  agility,  nearly  touching  wdth  its  dorsal  side  the  skin 
of  the  hand  upon  which  it  is  feeding.  Meanwhile,  the  hungry  para- 
site feeds  ravenously." 

"It  is  interesting  to  note  the  peculiar  nervous  action  which  the 
rodent  fleas  exhibit  immediately  when  the  feeding  process  is  com- 
pleted or  when  disturbed  during  the  biting.  Even  while  the  rostrum 
is  inserted  to  the  fullest  the  parasite  shakes  its  head  spasmodically ; 
in  a  twinkling  the  mouth  is  withdrawn  and  then  the  flea  hops  away." 

A  habit  of  fleas  which  we  shall  see  is  of  significance  in  considering 
their  agency  in  the  spread  of  bubonic  plague,  is  that  of  ejecting  blood 
from  the  anus  as  they  feed. 

Fleas  are  famous  for  their  jumping  powers,  and  in  control  measures 
it  is  of  importance  to  determine  their  ability  along  this  line.  It  is 
often  stated  that  they  can  jump  about  four  inches,  or,  according  to 
the  Indian  Plague  Commission  Xenopsylla  cheopis  cannot  hop  farther 
than  five  inches.  Mitzmain  (19 lo)  conducted  some  careful  experi- 
ments in  which  he  found  that  the  human  flea,  Pulex  irritans,  was 
able  to  jump  as  far  as  thirteen  inches  on  a  horizontal  plane.  The 
mean  average  of  five  specimens  permitted  to  jump  at  will  was  seven 
and  three-tenths  inches.  The  same  species  was  observed  to  jump 
perpendicularly  to  a  height  of  at  least  seven  and  three-fourths  inches. 
Other  species  were  not  able  to  equal  this  record. 

The  effect  of  the  bite  of  fleas  on  man  varies  considerably  accord- 
ing to  the  individual  susceptibility.  According  to  Patton  and  Cragg, 
this  was  borne  out  in  a  curious  manner  by  the  experiments  of  Chick 
and  Martin.  "In  these,  eight  human  hosts  were  tried;  in  seven, 
little  or  no  irritation  was  produced,  while  in  one  quite  severe  inflam- 
mation was  set  up  around  each  bite."  Of  two  individuals,  equally 
accustomed  to  the  insects,  going  into  an  infested  room,  one  may  be 
literally  tormented  by  them  while  the  other  will  not  notice  them. 


Siphonaptera,  or  Fleas  125 

Indeed  it  is  not  altogether  a  question  of  susceptibility,  for  fleas  seem 
to  have  a  special  predilection  for  certain  individuals.  The  typical 
itching  wheals  produced  by  the  bites  are  sometimes  followed,  especi- 
ally after  scratching,  by  inflammatory  papules. 

The  itching  can  be  relieved  by  the  use  of  lotions  of  carbolic  acid 
(2-3  per  cent),  camphor,  menthol  lotion,  or  carbolated  vaseline. 
If  forced  to  sleep  in  an  infested  room,  protection  from  attacks  can 
be  in  a  large  measure  gained  by  sprinkling  pyre  thrum,  bubach,  or 
California  insect  powder  between  the  sheets.  The  use  of  camphor, 
menthol,  or  oil  of  eucalyptus,  or  oil  of  pennyroyal  is  also  said  to  afford 
protection  to  a  certain  extent. 

In  the  Eastern  United  States  the  occurrence  of  fleas  as  household 
pests  is  usually  due  to  infested  cats  and  dogs  which  have  the  run  of 
the  house.  We  have  seen  that  the  eggs  are  not  attached  to  the  host 
but  drop  to  the  floor  when  they  are  laid.  Verrill,  cited  by  Osbom, 
states  that  on  one  occasion  he  was  able  to  collect  fully  a  teaspoonful 
of  eggs  from  the  dress  of  a  lady  in  whose  lap  a  half -grown  kitten  had 
been  held  for  a  short  time.  Patton  and  Cragg  record  seeing  the 
inside  of  a  hat  in  which  a  kitten  had  spent  the  night,  so  covered  with 
flea  eggs  that  it  looked  "as  if  it  had  been  sprinkled  with  sugar  from 
a  sifter."  It  is  no  wonder  that  houses  in  which  pets  live  become 
overrun  with  the  fleas. 

One  of  the  first  control  measures,  then,  consists  in  keeping  such 
animals  out  of  the  house  or  in  rigorously  keeping  them  free  from  fleas. 
The  latter  can  best  be  accomplished  by  the  use  of  strong  tar  soap 
or  Armour's  "Flesope,"  which  may  be  obtained  from  most  druggists. 
The  use  of  a  three  per  cent  solution  of  creolin,  approximately  four 
teaspoonfuls  to  a  quart  of  warm  water,  has  also  been  recommended. 
While  this  is  satisfactory  in  the  case  of  dogs,  it  is  liable  to  sicken  cats, 
who  will  lick  their  fur  in  an  effort  to  dry  themselves.  Howard 
recommends  thoroughly  rubbing  into  the  fur  a  quantity  of  pyrethrum 
powder.  This  partially  stupifies  the  fleas  which  should  be  promptly 
swept  up  and  burned. 

He  also  recommends  providing  a  rug  for  the  dog  or  cat  to  sleep 
on  and  giving  this  rug  a  frequent  shaking  and  brushing,  afterwards 
sweeping  up  and  burning  the  dust  thus  removed. 

Since  the  larvae  of  fleas  are  very  susceptible  to  exposure,  the  use 
of  bare  floors,  with  few  rugs,  instead  of  carpets  or  matting,  is  to  be 
recommended.  Thorough  sweeping,  so  as  to  allow  no  accumulation 
of  dust  in  cracks  and  crevices  will  prove  efficient.     If  a  house  is  once 


126  Parasitic  Arthropoda 

infested  it  may  be  necessary  to  thoroughly  scrub  the  floors  with  hot 
soapsuds,  or  to  spray  them  with  gasoUne.  If  the  latter  method  is 
adopted,  care  must  be  taken  to  avoid  the  possibility  of  fire. 

To  clear  a  house  of  fleas  Skinner  recommends  the  use  of  flake 
naphthalene.  In  a  badly  infested  house  he  took  one  room  at  a  time, 
scattering  on  the  floor  five  pounds  of  flake  naphthalene,  and  closed 
it  for  twenty-four  hours.  It  proved  to  be  a  perfect  and  effectual 
remedy  and  very  inexpensive,  as  the  naphthalene  could  be  swept  up 
and  transferred  to  other  rooms.  Dr.  Skinner  adds,  "so  far  as  I  am 
concerned,  the  flea  question  is  solved  and  if  I  have  further  trouble 
I  know  the  remedy.     I  intend  to  keep  the  dog  and  cat." 

The  late  Professor  Slingerland  very  effectively  used  hydrocyanic 
acid  gas  fumigation  in  exterminating  fleas  in  houses.  In  one  case, 
where  failure  was  reported,  he  found  on  investigation  that  the  house 
had  become  thoroughly  reinfested  from  pet  cats,  which  had  been  left 
untreated.     Fumigation  with  sulphur  is  likewise  efficient. 

The  fact  that  adult  fleas  are  usually  to  be  found  on  the  floor, 
when  not  on  their  hosts,  was  ingeniously  taken  advantage  of  by 
Professor  S.  H.  Gage  in  ridding  an  animal  room  at  Cornell  University 
of  the  pests.  He  swathed  the  legs  of  a  janitor  with  sticky  fly-paper 
and  had  him  walk  back  and  forth  in  the  room.  Large  numbers  of 
the  fleas  were  collected  in  this  manner. 

In  some  parts  of  the  southern  United  States  hogs  are  commonly 
infested  and  in  turn  infest  sheds,  bams  and  even  houses.  Mr.  H.  E. 
Vick  informs  us  that  it  is  a  common  practice  to  turn  sheep  into  barn- 
lots  and  sheds  in  the  spring  of  the  year  to  collect  in  their  wool,  the 
fleas  which  abound  in  th^ge  places  after  the  hogs  have  been  turned 
out. 

It  is  a  common  belief  that  adult  fleas  are  attracted  to  fresh  meat 
and  that  advantage  of  this  can  be  taken  in  trapping  them.  Various 
workers,  notably  Mitzman  (1910),  have  shown  that  there  is  no  basis 
for  such  a  belief. 

The  true  chiggers — The  chigoes,  or  true  chiggers,  are  the  most 
completely  parasitic  of  any  of  the  fleas.  Of  the  dozen  or  more  known 
species,  one  commonly  attacks  man.  This  is  Dermatophilus  penetrans, 
more  commonly  knowTi  as  Sarcopsylla  penetrans  or  Pulex  penetrans. 

This  species  occurs  in  Mexico,  the  West  Indies,  Central  and  South 
America.  There  are  no  authentic  records  of  its  occurrence  in  the 
United  States  although,  as  Baker  has  pointed  out,  there  is  no  reason 


The  True  Chiggers 


127 


why  it  should  not  become  established  in  Florida  and  Texas.  It  is 
usually  believed  that  Brazil  was  its  original  home.  Sometime  about 
the  middle  of  the  nineteenth  century  it  was  introduced  into  West 
Africa  and  has  spread  across  that  continent. 

The  males  and  the  immature  females  of  Dermatophilus  penetrans 
(fig.  93)  closely  resemble  those  of  other  fleas.  They  are  very  active 
little  brown  insects  about  1-1.2  mm.  in  size,  which  live  in  the  dust  of 
native  huts  and  stables,  and  in  dry,  sandy  soil.  In  such  places  they 
■often  occur  in  enormous  numbers  and  become  a  veritable  plague. 

They  attack  not  only  man  but  various  animals.  According  to 
Castellani  and  Chalmers,  "  Perhaps  the  most  noted  feature  is  the  way 


93.     Dermatophilus  penetrans.     Much  enlarged.     After  Karsten. 

in  which  it  attacks  pigs.  On  the  Gold  Coast  it  appeared  to  be  largely 
kept  in  existence  by  these  animals.  It  is  very  easily  captured  in 
the  free  state  by  taking  a  little  pig  with  a  pale  abdomen,  and  placing 
it  on  its  back  on  the  ground  on  which  infected  pigs  are  living.  After 
watching  a  few  moments,  a  black  speck  will  appear  on  the  pig's 
abdomen,  and  quickly  another  and  another.  These  black  specks  are 
jiggers  which  can  easily  be  transferred  to  a  test  tube.  On  examina- 
tion they  wdll  be  found  to  be  males  and  females  in  about  equal 
numbers." 

Both  the  males  and  females  suck  blood.  That  which  characterizes 
this  species  as  distinguished  from  other  fleas  attacking  man  is  that 
when  the  impregnated  female  attacks  she  burrows  into  the  skin 
and  there  swells  until  in  a  few  days  she  has  the  size  and  appearance  of 
a     small  pea  (fig.  94).     Where  they  are  abundant,  hundreds  of  the 


128 


Parasitic  Arthropoda 


94.     Dermatophilus  penetrans,  gravid  female.     After  Moniez. 

pests  may  attack  a  single  individual  (fig.  95).     Here  they  lie  with  the 
apex  of  the  abdomen   blocking  the  opening.     According  to   Fiille- 

born  (1908)  they  do  not 
penetrate  beneath  the 
epidermis.  The  eggs  are 
not  laid  in  the  flesh  of 
the  victim,  as  is  some- 
times stated,  but  are 
expelled  through  this 
opening.  The  female 
then  dies,  withers  and 
falls  away  or  is  expelled 
by  iilceration.  Accord- 
ing to  Brumpt,  she  first 
quits  the  skin  and  then, 
falling  to  the  ground, 
deposits  her  eggs.  The 
subsequent  develop- 
ment in  so  far  as  known, 
is  Hke  that  of  other  fleas. 
The  chigoe  usually 
enters  between  the  toes, 
the  skin  about  the  roots 
of  the  iiails,  or  the  soles 


95. 


Chiggers  in  the   sole  of  foot  of   man.     Manson's 
Tropical  Diseases.     Permission  of  Cassell  and  Co. 


Siphonaptera,  or  Fleas 


129 


of  the  feet,  although  it  may  attack  other  parts  of  the  body.  Mense 
records  the  occurrence  in  folds  of  the  epidermis,  as  in  the  neighbor- 
hood of  the  anus.  They  give  rise  to  irritation 
and  unless  promptly  and  aseptically  removed 
there  often  occurs  pus  formation  and  the 
development  of  a  more  or  less  serious  abscess. 
Gangrene  and  even  tetanus  may  ensue. 

Treatment  consists  in  the  careful  removal 
of  the  insect,  an  operation  more  easily  accom- 
plished a  day  or  two  after  its  entrance,  than 
at  first,  when  it  is  unswollen.  The  ulcerated 
point  should  then  be  treated  with  weak  car- 
bolic acid,  or  tincture  of  iodine,  or  dusted 
thoroughly  with  an  antiseptic  powder. 

Castellani  and  Chalmers  recommend  as 
prophylactic  measures,  keeping  the  house  clean  and  keeping  pigs, 
poultry,  and  cattle  away  therefrom.  "High  boots  should  be  used, 
and  especial  care  should  be  taken  not  to  go  to  a  ground  floor  bath- 
room with  bare  feet.  The  feet,  -especially  the  toes,  and  under  the 
nails,  should  be  carefully  examined  every  morning  to  see  if  any  black 


Echidnophaga  gallinacea. 


97.     Echidnophaga  gallinacea  infesting  head  of  chicken.     After  Enderlein. 


dots  can  be  discovered,  when  the  jigger  should  be  at  once  removed, 
and  in  this  way  suppuration   wall  be  prevented.     It  is  advisable, 


130  Parasitic  Arthropoda 

also,  to  sprinkle  the  floors  with  carbolic  lotion,  Jeyes'  fluid,  or  with 
pyrethrum  powder,  or  with  a  strong  infusion  of  native  tobacco,  as 
recommended  by  Law  and  Castellani." 

Echidnophaga  gallinacea  (fig.  96)  is  a  widely  distributed  Hectopsyl- 
lid  attacking  poultry  (fig.  97).  It  occiirs  in  the  Southern  and  South- 
western United  States  and  has  been  occasionally  reported  as  attack- 
ing man,  especially  children.  It  is  less  highly  specialized  than 
Dermatophilus  penetrans,  and  does  not  ordinarily  cause  serious 
trouble  in  man. 


CHAPTER  IV 
ACCroENTAL   OR   FACULTATIVE   PARASITES 

In  addition  to  the  many  species  of  Arthropods  which  are  normally 
parasitic  on  man  and  animals,  there  is  a  considerable  number  of  those 
which  may  be  classed  as  accidental  or  facultative  parasites. 

Accidental  or  facultative  parasites  are  species  which  are  normally 
free-living,  but  which  are  able  to  exist  as  parasites  when  accidentally 
introduced  into  the  body  of  man  or  other  animal.  A  wide  range  of 
forms  is  included  under  this  grouping. 

ACARINA 

A  considerable  number  of  mites  have  been  reported  as  accidental 
or  even  normal,  endoparasites  of  man,  but  the  authentic  cases  are" 
comparatively  few. 

In  considering  such  reports  it  is  well  to  keep  in  mind  von  Siebold's 
warning  that  in  view  of  the  universal  distribution  of  mites  one  should 
be  on  his  guard.  In  vessels  in  which  animal  and  other  organic 
fluids  and  moist  substances  gradually  dry  out,  mites  are  very  abund- 
anth^  found.  If  such  vessels  are  used  without  very  careful  prelimi- 
nary cleaning,  for  the  reception  of  evacuations  of  the  sick,  or  for  the 
reception  of  parts  removed  from  the  body,  such  things  may  be  readily 
contaminated  by  mites,  which  have  no  other  relation  whatever  to 
them. 

Nevertheless,  there  is  no  doubt  but  that  certain  mites,  normally 
free-living,  have  occurred  as  accidental  parasites  of  man.  Of  these 
the  most  commonly  met  with  is  Tyroglyphus  siro,  the  cheese-mite. 

Tyroglyphus  siro  is  a  small  mite  of  a  whitish  color.  The  male 
measures  about  soo\i.  long  by  2505^  wide,  the  female  slightly  larger. 
They  live  in  cheese  of  almost  any  kind,  especially  such  as  is  a  Httle 
■decayed.  "The  individuals  gather  together  in  winter  in  groups  or 
heaps  in  the  hollows  and  chinks  of  the  cheese  and  there  remain 
motionless.  As  soon  as  the  temperature  rises  a  little,  they  gnaw 
away  at  the  cheese  and  reduce  it  to  a  powder.  The  powder  is  com- 
posed of  excrement  having  the  appearance  of  little  grayish  microscopic 
balls;  eggs,  old  and  new,  cracked  and  empty;  larvae,  nymphs,  and 
perfect  mites,  cast  skins  and  fragments  of  cheese,  to  which  must  be 
added  numerous  spores  of  microscopic  fungi." — Murray. 

131 


132  Accidental  or  Facultative  Parasites 

Tyroglyphus  siro,  and  related  species,  have  been  found  many 
times  in  human  feces,  under  conditions  which  preclude  the  explana- 
tion that  the  contamination  occurred  outside  of  the  body.  They 
have  been  supposed  to  be  the  cause  of  dysentery,  or  diarrhoea,  and 
it  is  probable  that  the  Acarus  dysenterice  of  Linnaeus,  and  Latreille, 
was  this  species.  However,  there  is  little  evidence  that  the  mites 
cause  any  noteworthy  symptoms,  even  when  taken  into  the  body 
in  large  numbers. 

Histiogaster  spermaticus  (fig.  152)  is  a  Tyroglyphid  mite  which 
was  reported  by  Trouessart  (1902)  as  having  been  found  in  a  cyst 
in  the  groin,  adherent  to  the  testis.  When  the  cyst  was  punctured, 
it  yielded  about  two  ounces  of  opalescent  fluid  containing  spermatozoa 
and  numerous  mites  in  all  stages  of  development.  The  evidence 
indicated  that  a  fecundated  female  mite  had  been  introduced  into 
the  urethra  by  means  of  an  unclean  catheter.  Though  Trouessart 
reported  the  case  as  that  of  a  Sarcoptid,  Banks  places  the  genus 
Histiogaster  with  the  Tyroglyphidae.  He  states  that  our  species 
feeds  on  the  oyster-shell  bark  louse,  possibly  only  after  the  latter  is 
dead,  and  that  in  England  a  species  feeds  within  decaying  reeds. 

Nephrophages  sanguinarius  is  a  peculiarly-shaped,  angular  mite 
which  was  found  by  Miyake  and  Scriba  (1893)  for  eight  successive 
days  in  the  urine  of  a  Japanese  suffering  from  fibrinuria.  Males, 
.117  mm.  long  by  .079  mm.  wide,  females  .36  mm.  by  .12  mm., 
and  eggs  were  found  both  in  the  spontaneously  emitted  urine  and  in 
that  drawn  by  means  of  a  catheter.  All  the  mites  found  were  dead. 
The  describers  regarded  this  mite  as  a  true  endoparasite,  but  it  is 
more  probable  that  it  should  be  classed  as  an  accidental  parasite. 

Myriapoda 

There  are  on  record  a  number  of  cases  of  myriapods  occurring  as 
accidental  parasites  of  man.  The  subject  has  been  treated  in  detail 
by  Blanchard  (1898  and  1902),  who  discussed  forty  cases.  Since 
then  at  least  eight  additions  have  been  made  to  the  list. 

Neveau-Lamaire  (1908)  lists  thirteen  species  implicated,  repre- 
senting eight  different  genera.  Of  the  Chilognatka  there  are  three, 
Julus  terresiris,  J.  londinensis  and  Polydesmus  complanatus.  The 
remainder  are  CJiilopoda,  namely,  Lithobius  forficatus,  L.  malenops, 
Geophilus  carpophagus,  G.  electricus,  G.  similis,  G.  cephalicus,  SciUigera 
coleoptrata,  Himantarium  gervaisi,  ChcBtechelyne  vesuviana  and 
Stigmatogaster  suhterraneus . 


Myriapoda  133 

The  majority  of  the  cases  relate  to  infestation  of  the  nasal  fossae, 
or  the  frontal  sinus,  but  intestinal  infestation  also  occurs  and  there 
is  one  recorded  case  of  the  presence  of  a  species  in  Julus  (fig.  13)  in 
the  auditory  canal  of  a  child. 

In  the  nose,  the  myriapods  have  been  known  to  live  for  months 
and  according  to  some  records,  even  for  years.  The  symptoms 
caused  by  their  presence  are  inflammation,  with  or  without  increased 
flow  of  mucus,  itching,  more  or  less  intense  headache,  and  at  times 
general  s^onptoms  such  as  vertigo,  delirium,  convulsions,  and  the 
like.  These  symptoms  disappear  suddenly  when  the  parasites  are 
expelled. 

In  the  intestine  of  man,  myriapods  give  rise  to  obscure  s\TTiptoms 
suggestive  of  infestation  by  parasitic  worms.  In  a  case  reported  by 
Verdun  and  Bruyant  (191 2),  a  child  twenty  months  of  age  had  been 
affected  for  fifteen  days  by  digestive  disturbances  characterized  by 
loss  of  appetite,  nausea  and  vomiting.  The  latter  had  been  partic- 
ular!}^ pronounced  for  three  days,  when  there  was  discovered  in  the 
midst  of  the  material  expelled  a  living  myriapod  of  the  species 
ChcBtechelyne  vesuviana.  Anthelminthics  had  been  administered 
without  result.  In  some  of  the  other  cases,  the  administration  of 
such  dings  had  resulted  in  the  expulsion  of  the  parasite  through  the 
anus. 

One  of  the  extreme  cases  on  record  is  that  reported  by  Shipley 
(1914).  Specimens  of  Geophilus  gorizensis  {=  G.  subterraneus) 
'were  vomited  and  passed  by  a  woman  of  68  years  of  age.  Some  of 
the  centipedes  emerged  through  the  patient's  nose,  and  it  must  be 
mentioned  that  she  was  also  suffering  from  a  round  worm.  One  of 
her  doctors  was  of  the  opinion  that  the  centipedes  were  certainly 
breeding  inside  the  lady's  intestines,  and  as  many  as  seven  or  eight, 
sometimes  more,  were  daily  leaving  the  alimentary  canal." 

"According  to  her  attendant's  statements  these  centipedes  had 
left  the  body  in  some  hundreds  during  a  period  of  twelve  or  eighteen 
months.  Their  presence  produced  vomiting  and  some  haematemesis, 
and  treatment  with  thymol,  male-fern  and  turpentine  had  no  effect 
in  removing  the  creatures." 

The  clinical  details,  as  supplied  by  Dr.  Theodore  Thompson  were 
as  follows : 

"Examined  by  me  July,  191 2,  her  tongue  was  dry  and  glazed. 
There  was  bleeding  taking  place  from  the  nose  and  I  saw  a  living 
centipede  she  had  just  extracted  from  her  nostril.     Her  heart,  lungs 


134  Accidental  or  Facultative  Parasites 

and  abdomen  appeared  normal.  She  was  not  very  wasted,  and  did 
not  think  she  had  lost  much  flesh,  nor  was  there  any  marked  degree 
of  anemia." 

Shiple}^  gives  the  following  reasons  for  believing  it  impossible 
that  these  centipedes  could  have  multiplied  in  the  patient's  intestine. 
"The  breeding  habits  of  the  genus  Geophilus  are  peculiar,  and  ill 
adapted  for  reproducing  in  such  a  habitat.  The  male  builds  a  small 
web  or  nest,  in  which  he  places  his  sperm,  and  the  female  fertilizes 
herself  from  this  nest  or  web,  and  when  the  eggs  are  fertilized  they 
are  again  laid  in  a  nest  or  web  in  which  they  incubate  and  in  two  or 
three  weeks  hatch  out.  The  young  Geophilus  differ  but  very  little 
from  the  adult,  except  in  size.  It  is  just  possible,  but  improbable, 
that  a  clutch  of  eggs  had  been  swallowed  by  the  host  when  eating 
some  vegetables  or  fruit,  but  against  this  is  the  fact  that  the  Geophilus 
does  not  lay  its  eggs  upon  vegetables  or  fruit,  but  upon  dry  wood  or 
earth.  The  egg-shell  is  very  tough  and  if  the  eggs  had  been  swallowed 
the  egg-shells  could  certainly  have  been  detected  if  the  dejecta  were 
examined.  The  specimens  of  the  centipede  showed  very  little  signs 
of  being  digested,  and  it  is  almost  impossible  to  reconcile  the  story 
of  the  patient  with  what  one  knows  of  the  habits  of  the  centipedes." 

In  none  of  the  observed  cases  have  there  been  any  clear  indica- 
tions as  to  the  manner  of  infestation.  It  is  possible  that  the  m^'ria- 
pods  have  been  taken  up  in  uncooked  fruit  or  vegetables. 

Lepidopterous   Larv^ 

Scholeciasis — Hope  (1837)  brought  together  six  records  of  infesta- 
tion of  man  by  lepidopterous  larvas  and  proposed  to  apply  the  name 
scholeciasis  to  this  type  of  parasitism.  The  clearest  case  was  that 
of  a  young  boy  who  had  repeatedly  eaten  raw  cabbage  and  who 
vomited  larvae  of  the  cabbage  butterfly,  Pieris  brassicce.  Such  cases 
are  extremely  rare,  and  there  are  few  reliable  data  relative  to  the 
subject.  In  this  connection  it  may  be  noted  that  Spuler  (1906)  has 
described  a  moth  whose  larvae  live  as  ectoparasites  of  the  sloth. 

COLEOPTERA 

Canthariasis — By  this  term  Hope  designated  instances  of  acci- 
dental parasitism  by  the  larvae  or  adults  of  beetles.  Reports  of 
such  cases  are  usually  scouted  by  parasitologists  but  there  seems  no 
good  basis  for  wholly  rejecting  them.  Cobbold  refers  to  a  half 
dozen  cases  of  accidental  parasitism  by  the  larvae  of  Blaps  mortisaga. 


Dipterous  Larvce 


135 


98.     Larva  of  Pinphila  casei.     Caudal  aspect  of  larva. 
Posterior  stigmata. 


In  one  of  these  cases  upwards  of  1200  larvae  and  several  perfect 
insects  were  said  to  have  been  passed  per  anum.     French  (1905) 

reports  the  case  of  a  man 
who  for  a  considerable  period 
voided  adult  living  beetles 
of  the  species  Nitidula 
bipustulata.  Most  of  the 
other  cases  on  record  relate 
to  the  larvae  of  DermestidoB 
(larder  beetles  et  al.)  or 
TenehrionidcB  (meal  infesting  species).  Infestation  probably  occurs 
through  eating  raw  or  imperfectly  cooked  foods  containing  eggs  or 
minute  larvae  of  these  insects. 

Brumpt  cites  a  curious  case  of  accidental  parasitism  by  a  coleopter- 
ous larva  belonging  to  the  genus  Necrohia.  This  larva  was  extracted 
from  a  small  tumor,  several  millimeters  long,  on  the  surface  of  the 
conjunctiva  of  the  eye.  The  larvae  of  this  genus  ordinarily  live  in 
decomposing  flesh  and  cadavers. 

Dipterous   Larv^ 

Myasis — By  this  term  (spelled  also  myiasis,  and  myiosis),  is 
meant  parasitism  by  dipterous  larvae.  Such  parasitism  may  be 
normal,  as  in  the  cases  already  described  under  the  heading  parasitic 
Diptera,  or  it  may  be  facultative,  due  to  free-living  larvae  being 
accidentally  introduced 
into  wounds  or  the  body- 
cavities  of  man.  Of  this 
latter  type,  there  is  a 
multitude  of  cases  on 
record,  relating  to  com- 
paratively few  species. 
The  literatiire  of  the  sub- 
ject, like  that  relating 
to  facultative  parasitism 
in  general,  is  unsatis- 
factory, for  most  of  the 
determinations  of  species 
have    been    very    loose. 

Indeed,  so  little  has  been  known  regarding  the  characteristics  of 
the  larvae  concerned  that  in  many  instances  they  could  not  be  exactly 


99.     Plophila  casei.     After  Graham-Smith. 


136  Accidental  or  Facultative  Parasites 

determined.  Fortunately,  several  workers  have  undertaken  com- 
parative studies  along  this  line.  The  most  comprehensive  publica- 
tion is  that  of  Banks  (19 12),  entitled  "The  structure  of  certain  dip- 
terous larv^se,  with  particular  reference  to  those  in  human  food." 

Without  attempting  an  exhaustive  list,  we  shall  discuss  here  the 
more  important  species  of  Diptera  whose  larv^ae  are  known  to  cause 
myasis,  either  external  or  internal.  The  following  key  will  serve 
to  determine  those  most  likely  to  be  encountered.  The  writers 
woidd  be  glad  to  examine  specimens  not  readily  identifiable,  if 
accompanied  by  exact  data  relative  to  occiu"rence. 

a.  Body  more  or  less  flattened,  depressed;  broadest  in  the  middle,  each  segment 

with  dorsal,  lateral,  and  ventral  fleshy  processes,  of  which  the  laterals, 

at  least,  are  more  or  less  spiniferous  (fig.   loi).   Fannia  {  =  Hotnalomyia). 

In  F.  canicularis  the  dorsal  processes  are  nearly  as  long  as  the  laterals; 

in  F.  scalaris  the  dorsal  processes  are  short  spinose  tubercles. 

aa.  Body  cylindrical,   or  slender  conical  tapering  toward  the  head;     without 

fleshy  lateral  processes  (fig.  105). 
h.  With  the  posterior  stigmata  at  the  end  of  shorter  or  longer  tubercles,  or  if  not 
placed  upon  tubercles,  then  not  in  pit;  usually  without  a  "marginal  button" 
and  without  a  chitinous  ring  surrounding  the  three  slits;   the  slits  narrowly 
or  broadly  oval,  not  bent  (fig.  171  i).     A  caly pirate  muscida  and  some  species 
of  AnihomyiidcE.     To  this  group  belong  the  cheese  skipper  {Piophila  casei, 
figs.  98,  99),  the  pomace-fly  {Drosophila  ampelophila) ,  the  apple  maggot 
{Rhagolelis  pomonella),  the  cherry  fruit  fly  (Rhagoletis  cingulata),  the  small 
dung   fly  {Sepsis  violacea,  fig.  170),  the  beet  leaf -miner  {Pegomyia  vicina, 
fig.  171  i),  the  cabbage,  bean  and  onion  maggots  (Phorbia  spp.)  et.  al. 
bb.  Posterior  stigmata  of  various  forms,  if  the  slits  are  narrowly  oval  (fig.  171) 
then  they  are  surrounded  by  a  chitin  ring  which  may  be  open  ventro- 
mesally. 

c.  Integument  leathery  and  usually  strongly  spinulose;    larv^  hypodermatic  or 

endoparasitic Bot  flies  (fig.   171,  f,  g,  k). — Oestridce 

cc.  Integument  not  leathery  and  (except  in  Protocalliphora)  spinulae    restricted 
to  transverse  patches  near  the  incisures  of  the  segments. 

d.  The  stigmal  plates  in  a  pit;    the  lip-like  margin  of  the  pit  with  a  number  of 

fleshy  tubercles;   chitin  of  the  stigma  not  complete;    open  ventro-mesaUy, 

button  absent  (fig.  171  e) Flesh  flies. — Sarcophaga 

dd.  Stigmata  not  in  a  pit. 

e.  The  chitin  ring  open  ventra-mesally ;    button  absent   (fig.    171   c).     Screw- 

worm   fly Chrysotnyia 

ee.  The  chitin  ring  closed. 

/.  Slits  of  the  posterior  stigmata  straight;  marginal  "button"  present  (fig.  171  b); 
two  distinct  mouth  hooks,  fleshy  tubercles  around  the  anal  area.  Phormia 
(fig.  171  f),  Lucilia  and  Calliphora  (fig.  172,  a,  b),  Protocalliphora  (fig.  171,  j), 
Cynomyia   (fig.    171,   a).     Blow  flies,  bluebottle  flies Calliphorince 


Dipterous  Larvcs  137 

JJ.  Slits  of  the  posterior  stigmata  sinuous  or  bent.     Subfamily  Muscinae. 
g.  Slits  of  the  posterior  stigmata  bent;    usually  two  mouth  hooks.     Muscina 
stahulans  (fig.  171,  /),  Muscina  similis,  Myiospila  meditatiinda   (fig.  172,  i), 
and  some  of  the  higher  Anthomyiidcc. 
gg.  Slits  of  the  posterior  stigmata  sinuous;    mouth  hooks  usually  consolidated 
into  one.     The  house-fly   {Musca  domestica    fig.    171,    d),    the  stable  fly 
{Stomoxys  calcitrans)  the  horn  fly  {Lyperosia  irritans),  Pyrellia,  Pseudo- 
pyrellia,  Morellia,  Mesembrina.  Polietes,  et.  al.  (fig.  172  in  part). 

Eristalis — The  larvae  of  Eristalis  are  the  so-called  rat-tailed  mag- 
gots, which  develop  in  foul  water.  In  a  few  instances  these  larvae 
have  been  known  to  pass  through  the  human  alimentary-  canal 
uninjured.  Hall  and  Muir  (1913)  report  the  case  of  a  boy  five  years 
of  age,  who  had  been  ailing  for  ten  weeks  and  who  was  under  treat- 
ment for  indigestion  and  chronic  constipation.  For  some  time  he 
had  vomited  ever>i:hing  he  ate.  On  administration  of  a  vermifuge 
he  voided  one  of  the  rat-tailed  maggots  of  Eristalis.  He  admitted 
having  drurjJv  water  from  a  ditch  full  of  all  manner  of  rotting  matter. 
It  was  doubtless  through  this  that  he  became  infested.  It  is  worth 
noting  that  the  above  described  symptoms  ma^'  ha\'e  been  due  to 
other  organisms  or  substances  in  the  filthy  water. 

Piophila  casei,  the  cheese-fly  (fig.  99),  deposits  its  eggs  not  only 
in  old  cheeses,  but  on  ham,  bacon,  and  other  fats.  The  larvae  (fig.  98) 
are  the  well-known  cheese  skippers,  which  sometimes  occiu*  in  great 
abundance  on  certain  kinds  of  cheese.  Indeed,  some  people  have 
a  comfortable  theor^^  that  such  infested  cheese  is  especially  good. 
Such  being  the  case,  it  is  small  wonder  that  this  species  has  been 
repeatedly  reported  as  causing  intestinal  myasis.  Thebault  (1901) 
describes  the  case  of  a  girl  who,  shortly  after  consuming  a  large  piece 
of  badly  infested  cheese,  became  ill  and  experienced  severe  pains 
in  the  region  of  the  navel.  Later  these  extended  through  the  entire 
alimentary  canal,  the  excrement  was  mixed  with  blood  and  she 
suffered  from  vertigo  and  severe  headaches.  During  the  four  fol- 
lowing days  the  girl  felt  no  change,  although  the  excretion  of  the  blood 
gradually  diminished  and  stopped.  On  the  fourth  day  she  voided 
two  half-digested  larvse  and,  later,  seven  or  eight,  of  which  two  were 
alive  and  moving. 

That  these  symptoms  ma>'  be  directly  attributed  to  the  larvae, 
or  "skippers," has  been  abundantly  shown  by  experimental  evidence. 
Portschinsky  cites  the  case  of  a  dog  fed  on  cheese  containing  the 
larvae.  The  animal  suffered  much  pain  and  its  excrement  contained 
blood.    On  post  mortem  it  was  found  that  the  small  intestine  through- 


138  Accidental  or  Facultative  Parasites 

out  almost  its  entire  length  was  marked  by  bloody  bruises.  The 
papillee  on  these  places  were  destroyed,  although  the  walls  were 
not  entirely  perforated.  In  the  appendix  were  found  two  or  three 
dead  larv^ae.  Alessandri  (19 10)  has  likewise  shown  that  the  larvae- 
cause  intestinal  lesions. 

According  to  Graham-Smith,  Austen  (191 2)  has  recorded  a  case 
of  myasis  of  the  nose,  attended  with  a  profuse  watery  discharge  of 
several  weeks  duration  and  pain,  due  to  the  larv^as  of  Piophila  casei. 
Anthyomyiidae — The  characteristic  larvae  of  two  species  of  Fannia 
{  =  Homalomyia  or  Anthomyia,  in  part)  (fig.  loi)  are  the  most  com- 
monly reported  of  dip- 
terous lar\^3e  causing  intes- 
tinal myasis.  Hewitt 
(19 1 2)  has  presented  a 
valuable  study  of  the  bio- 
nomics and  of  the  larva? 
of  these  flies,  a  type  of 
what  is  needed  for  all  the 
species  concerned  in  my- 
asis. We  have  seen  two 
cases  of  their  having  been 
passed  in  stools,  without  having  caused  any  special  symptoms. 
In  other  instances  their  presence  in  the  alimentary^  canal  has  given 
rise  to  symptoms  vaguely  described  as  those  of  tapeworm  infestation, 
or  helminthiasis.  More  specifically,  they  have  been  described  as 
causing  vertigo,  severe  headache,  nausea  and  vomiting,  severe 
abdominal  pains,  and  in  some  instances,  bloody  diarrhoea. 

One  of  the  most  striking  cases  is  that  reported  by  Blankmeyer 
(19 14),  of  a  woman  whose  illness  began  fourteen  years  previously 
with  nausea  and  vomiting.  After  several  months  of  illness  she  began 
passing  larv^se  and  was  compelled  to  resort  to  enemas.  Three  years 
previous  to  the  report,  she  noticed  frequent  shooting  pains  in  the 
rectal  region  and  at  times  abdominal  tenderness  was  marked.  There 
was  much  mucus  in  the  stools  and  she  "experienced  the  sensation 
of  larvas  crawling  in  the  intestine."  Occipital  headaches  were 
marked,  with  remissions,  and  constipation  became  chronic.  The 
appetite  was  variable,  there  was  a  bad  taste  in  the  mouth,  tongue 
furred  and  ridged,  and  red  at  the  edges.  Her  complexion  w^as  sal- 
low, and  general  nervousness  was  marked.  As  treatment,  there 
were  given  doses  of  magnesium  sulphate  before  breakfast  and  at 


100.     Fannia  canicularis  (x4).     After  Graham-Smith. 


AntkyomyiidcB 


139 


4  p.  M. ,  with  five  grain  doses  of  salol  four  times  a  day.  The  customary 
parasiticides  yielded  no  marked  benefit.  At  the  time  of  the  report 
the  patient  passed  from  four  to  fifty  larv^ae  per  day,  and  was  showing 
some  signs  of  improvement.  The  nausea  had  disappeared,  her 
nervousness  was  less  evident,  and  there  was  a  slight  gain  in  weight. 
The  case  was  complicated  by  various  other  disorders,  but  the 
symptoms  given  above  seem  to  be  in  large  part  attributable  to  the 
myasis.  There  is  nothing  in  the  case  to  justify  the  assumption 
that  larvae  were  continuously  present,  for  years.  It  seems  more 
reasonable  to  suppose  that  something  in  the  habits  of  the  patient 
favored  repeated  infestation.  Nevertheless,  a  study  of  the  various 
cases  of  intestinal  myasis  caused  by  these  and 
other  species  of  dipterous  larvae  seems  to  indi- 
cate that  the  normal  life  cycle  may  be  con- 
siderably prolonged  under  the  unusual  conditions. 
The  best  authenticated  cases  of  myasis  of  the 
urinary  passage  have  been  due  to  larvae  of 
Fannia.  Chevril  (1909)  collected  and  described 
twenty  cases,  of  which  seven  seemed  beyond 
doubt.  One  of  these  was  that  of  a  woman  of 
fifty -five  who  suffered  from  albuminuria,  and 
urinated  with  much  difficulty,  and  finally  passed 
thirty  to  forty  larvae  of  Fannia  canicularis. 

It  is  probable  that  infestation  usually  occilrs 
through  eating  partially  decayed  fruit  or  vege- 
tables on  which  the  flies  have  deposited  their 
eggs.  Wellman  points  out  that  the  flies  may 
deposit  their  eggs  in  or  about  the  anus  of 
persons  using  outside  privies  and  Hewitt 
believes  that  this  latter  method  of  infection  is  probably  the  common 
one  in  the  case  of  infants  belonging  to  careless  mothers.  "Such 
infants  are  sometimes  left  about  in  an  exposed  and  not  very  clean 
condition,  in  consequence  of  which  flies  are  readily  attracted  to  them 
and  deposit  their  eggs." 

Muscinae — The  larv^ae  of  the  common  house-fly,  Musca  domestica, 
are  occasionally  recorded  as  having  been  passed  with  the  feces  or 
vomit  of  man.  While  such  cases  may  occur,  it  is  probable  that  in 
most  instances  similar  appearing  larv^ae  of  other  insects  have  been 
mistakenly  identified. 


101. 


Larva  of  Fannia 
scalaris. 


140 


Accidental  or  Facultative  Parasites 


Muscina  stabulans  (x4).     After  Graham 
Smith. 


Muscina  stabulans  is  re- 
garded by  Portschinsky 
(19 13)  as  responsible  for 
many  of  the  cases  of  intesti- 
nal myasis  attributed  to  other 
species.  He  records  the  case 
of  a  peasant  who  suffered  from 
pains  in  the  lower  part  of  the 
breast  and  intestines,  and 
whose  stools  were  mixed  with 
blood .  From  November  until 
March  he  had  felt  particu- 
larly ill,  being  troubled  with 
nausea  and  vomiting  in  addi- 
tion to  the  pain  in  his  intestines.  In  March,  his  physician  prescribed 
injections  of  a  concentrated  solution  of  tannin,  which  resulted  in  the 
expulsion  of  fifty  living  lar\"a3  of  Muscina  stabulans.  Thereafter 
the  patient  felt  much  better,  although  he  suffered  from  intestinal 
catarrh  in  a  less  severe  form. 

Calliphorinae — Closely  related  to  the  Sarcophagidae  are  the 
Calliphorinoe.  to  which  group  belong  many  of  the  so-called  "blue 
bottle"  flies.  Their  larvae  feed  upon  dead  animals,  and  upon  fresh 
and  cooked  meat.  Those  of  Pro- 
tocalliphora,  already  mentioned, 
are  ectoparasitic  on  living  nestling 
birds.  Larvae  of  Lucilia,  we  have 
taken  from  tumors  on  living  turtles. 
To  this  sub-family  belongs  also 
Aucheromyia  luteola,  the  Congo 
floor  maggot.  Some  of  these, 
and  at  least  the  last  mentioned, 
are  confirmed,  rather  than  faculat- 
tive  parasites.  Various  species  of 
Calliphorinae  are  occassionally  met 
with  as  facultative  parasites  of 
man. 

Chrysomyia  macellaria,  the  screw  worm  fly  (fig.  107),  is  the  fly 
which  is  responsible  for  the  most  serious  cases  of  human  myasis  in 
the  United  States.     It  is  widely  distributed  in  the  United  States 


103.      Lucilia  caesar.  (x3).      After  Howard. 


Chrysomyia  macellaria 


141 


but  is  especially  abundant  in  the  south.  While  the  larvae  b  \  n 
decaying  matter  in  general,  they  so  commonly  breed  in  the  living 
flesh  of  animals  that  they  merit  rank  as  true  parasites.  The  females 
are  attracted  to  open  wounds  of  all  kinds  on  cattle  and  other  animals 
and  quickly  deposit  large  numbers  of  eggs.  Animals  which  have 
been  recently  castrated,  dehorned,  or  branded,  injured  b}^  barbed 
wire,  or  even  by  the  attacks  of  ticks  are  promptly  attacked  in  the 
regions  where  the  fly  abotmds.  Even  the  navel  of  young  calves  or 
discharges  from  the  vulva  of  cows  may  attract  the  insect. 

Not  infrequently  the  fly  attacks  man,  being  attracted  by  an  of- 
fensive breath,  a  chronic  catarrh,  or  a  purulent  discharge  from  the 
ears.     Most  common  are  the  cases  where  the  eggs  are  deposited  in 


C      B  A 

104.     Calliphora  erythrocephala.  (x6).     After  Graham-Smith. 

the  nostrils.  The  larvae,  which  are  hatched  in  a  day  or  two,  are 
provided  with  strong  spines  and  proceed  to  bore  into  the  tissues 
of  the  nose,  even  down  into  or  through  the  bone,  into  the  frontal 
sinus,  the  phar^^nx,  larynx,  and  neighboring  parts. 

Osbom  (1896)  quotes  a  number  of  detailed  accounts  of  the  attacks 
of  the  Chrysomyia  on  man.  A  vivid  picture  of  the  symptomology 
of  rhinal  myasis  caused  by  the  larvae  of  this  fly  is  given  by  Castellani 
and  Chalmers:  "vSome  couple  of  days  after  a  person  sufTering  from 
a  chronic  catarrh,  foul  breath,  or  ozsena,  has  slept  in  the  open  or  has 
been  attacked  by  a  fly  when  riding  or  dri\4ng, — i.e.,  when  the  hands 
are  engaged — signs  of  severe  catarrh  appear,  accompanied  with 
inordinate  sneezing  and  severe  pain  over  the  root  of  the  nose  or  the 
frontal  bone.  Quickly  the  nose  becomes  swollen,  and  later  the  face 
also  may  swell,  while  examination  of  the  nose  may  show  the  presence 


142 


Accidental  or  Facultative  Parasites 


of  the  larvae.  Left  untreated,  the  patient  rapidly  becomes  worse, 
and  pus  and  blood  are  discharged  from  the  nose,  from  which  an 
offensive  odor  issues.  Cough  appears  as  well  as  fever,  and  often 
some  delirium.  If  the  patient  lives  long  enough,  the  septum  of  the 
nose  may  fall  in,  the  soft  and  hard  palates  may  be  pierced,  the  wall 
of  the  pharynx  may  be  destroyed.  By  this  time,  however,  the  course 
of  the  disease  will  have  become  quite  evident  by  the  larvae  dropping 
out  of  the  nose,  and  if  the  patient  continues  to  live  all  the  larvae 
may  come  away  naturally." 

For  treatment  of  rhinal  myasis  these  writers  recommend  douch- 
ing the  nose  with  chloroform  water  or  a  solution  of  chloroform  in 
sweet  milk  (10-20  per  cent),  followed  by  douches  of  mild  antiseptics. 
Surgical  treatment  may  be  necessary. 


105.    Larva  of  a  flesh  fly  (Sarcophaga).i    Caudal  aspect.    Anterior  stigmata.     Pharyngeal  skeleton. 

Sarcophagidse — The  larvae  (fig.  105)  of  flies  of  this  family  usually 
feed  upon  meats,  but  have  been  found  in  cheese,  oleomargerine, 
pickled  herring,  dead  and  living  insects,  cow  dung  and  human  feces. 
Certain  species  are  parasitic  in  insects.  Higgins  (1890)  reported 
an  instance  of  "hundreds"  of  larvae  of  Sarcophaga  being  vomited  by  a 
child  eighteen  months  of  age.  There  was  no  doubt  as  to  their  origin 
for  they  were  voided  while  the  physician  was  in  the  room.  There 
are  many  other  reports  of  their  occurrence  in  the  alimentary  canal. 
We  have  recorded  elsewhere  (Riley,  1906)  a  case  in  which  some  ten 
or  twelve  larvae  of  Sarcophaga  were  found  feeding  on  the  diseased 
tissues  of  a  malignant  tumor.  The  tumor,  a  melanotic  sarcoma, 
was  about  the  size  of  a  small  walnut,  and  located  in  the  small  of  the 
back  of  an  elderly  lady.  Although  they  had  irritated  and  caused  a 
slight  hemorrhage,  neither  the  patient  nor  others  of  the  family  knew 


SarcophagidcB 


143 


of  their  presence.   Any  discomfort  which  they  had  caused^had  been 
attributed  to  the  sarcomatous  growth.     The  infestation'Toccurred 


106.     A  flesh  fly  (Sarcophaga),  (.X4).     After  Graham-Smith. 

in  mid-simimer.  It  is  probable  that  the  adult  was  attracted  by  the 
•odor  of  the  discharges  and  deposited  the  living  maggots  upon  the 
■diseased  tissues. 

According  to  Kiichenmeister,  Sarcophaga  carnaria  (fig.  106), 
attracted  by  the  odor,  deposits  its  eggs  and  larvae  in  the  vagina  of 
girls  and  women  when  they  lie  naked  in  hot  summer  days  upon  dirty 
clothes,  or  when  they  have  a  discharge  from  the  vagina.  In  malig- 
nant inflammations  of  the  eyes  the  larvae 
■even  nestle  imder  the  eyelids  and  in 
Egypt,  for  example,  produce  a  very 
serious  addition  to  the  effects  of  small- 
pox upon  the  cornea,  as  according  to 
Pruner,  in  such  cases  perforation  of  the 
•cornea  usually  takes  place. 

Wohlfartia  magnifica  is  another 
Sarcophagid  which  commonly  infests 
man  in  the  regions  where  it  is  abun- 
dant. It  is  found  in  all  Europe  but  is 
especially  common  in  Russia,  where 
Portschinsky  has  devoted  much  atten- 
tion to  its  ravages.  It  deposits  living 
larvae  in  wounds,  the  nasal  fossae,  the 

ears   and   the    eyes,    causing   injuries        "'^-    c^hrysomyia  maceiiaria.  (x3) 
•even  more  revolting  than  those  described  for  Chrysomyia. 


CHAPTER  V 

ARTHROPODS  AS  SIMPLE  CARRIERS  OF  DISEASE 

The  fact  that  certain  arthropods  are  poisonous,  or  may  affect  the 
heahh  of  man  as  direct  parasites  has  always  received  attention  in 
the  medical  literature.  We  come  now  to  the  more  modern  aspect 
of  our  subject, — the  consideration  of  insects  and  other  arthropods 
as  transmitters  and  disseminators  of  disease. 

The  simplest  way  in  which  arthropods  may  function  in  this 
capacity  is  as  simple  carriers  of  pathogenic  organisms.  It  is  con- 
ceivable that  any  insect  which  has  access  to,  and  comes  in  contact 
with  such  organisms  and  then  passes  to  the  food,  or  drink,  or  to  the 
body  of  man,  may  in  a  wholly  accidental  and  incidental  manner 
convey  infection.  That  this  occurs  is  abundantly  proved  by  the 
work  of  recent  years.  We  shall  consider  as  typical  the  case  against 
the  house-fly,  which  has  attracted  so  much  attention,  both  popular 
and  scientific.  The  excellent  general  treatises  of  Hewitt  (1910), 
Howard  (igii),  and  Graham-Smith  (19 13),  and  the  flood  of  bulletins 
and  popular  literature  render  it  unnecessary  to  consider  the  topic 
in  any  great  detail. 

The  House-fly  as  a  Carrier  of  Disease 

Up  to  the  past  decade  the  house-fly  has  usually  been  regarded  as  a 
mere  pest.  Repeatedly,  however,  it  had  been  suggested  that  it 
might  disseminate  disease.  We  have  seen  that  as  far  back  as  the 
sixteenth  century,  Mercurialis  suggested  that  it  was  the  agent  in  the 
spread  of  bubonic  plague,  and  in  1658,  Kircher  reiterated  this  view. 
In  1871,  Leidy  expressed  the  opinion  that  flies  were  probably  a  means 
of  communicating  contagious  diseases  to  a  greater  degree  than  was 
generally  suspected.  From  what  he  had  observed  regarding  gangrene 
in  hospitals,  he  thought  flies  should  be  carefully  excluded  from 
wounds.  In  the  same  year,  the  editor  of  the  London  Lancet,  referring 
to  the  belief  that  they  play  a  useful  r61e  in  purifying  the  air  said, 
"Far  from  looking  upon  them  as  dipterous  angels  dancing  attendance 
on  Hygeia,  regard  them  rather  in  the  light  of  winged  sponges  spread- 
ing hither  and  thither  to  carry  out  the  foul  behests  of  Contagion." 

These  suggestions  attracted  little  attention  from  medical  men,  for 
it  is  only  within  very  recent  years  that  the  charges  have  been  sup- 
ported by  direct   evidence.     Before  considering  this  evidence,  it  is 

144 


The  House-fly  as  a  Carrier  of  Disease  145 

necessary  that  we  define  what  is  meant  by  "house-fly"  and  that  we 
then  consider  the  life-history  of  the  insect. 

There  are  many  flies  which  are  occasionally  to  be  found  in  houses, 
but  according  to  various  counts,  from  95  per  cent  to  99  per  cent  of 
these  in  warm  weather  in  the  Eastern  United  States  belong  to  the 
one  species  Musca  domestica  (fig.  108).  This  is  the  dominant  house- 
fly the  world  o\'er  and  is  the  one  which  merits  the  name.  It  has  been 
well  characterized  by  Schiner  (1864),  whose  description  has  been 
freely  translated  by  Hewitt,  as  follows: 

"  Frons  of  male  occupying  a  fourth  part  of  the  breadth  of  the  head. 
Frontal  stripe  of  female  narrow  in  front,  so  broad  behind  that  it 
entirely  fills  up  the  width  of  the  frons.  The  dorsal  region  of  the 
thorax  dusty  grey  in  color  with  four  equally  broad  longitudinal 
stripes.  Scutellum  gray  with  black  sides.  The  light  regions  of 
the  abdomen  yellowish,  transparent,  the  darkest  parts  at  least  at 
the  base  of  the  ventral  side  yellow.  The  last  segment  and  a  dorsal 
line  blackish  brown.  Seen  from  behind  and  against  the  light,  the 
whole  abdomen  shimmering  yellow,  and  only  on  each  side  of  the 
dorsal  line  on  each  segment  a  dull  transverse  band.  The  lower  part 
of  the  face  silky  yellow,  shot  with  blackish  brown.  Median  stripe 
velvety  black.  Antennae  brown.  Palpi  black.  Legs  blackish 
brown.  Wings  tinged  with  pale  gray  with  yellowish  base.  The 
female  has  a  broad  velvety  back,  often  reddishly  shimmering  frontal 
stripe,  which  is  not  broader  at  the  anterior  end  than  at  the  bases  of 
the  antennae,  but  become  so  very  much  broader  above  that  the  light 
dustiness  of  the  sides  is  entirely  obliterated.  The  abdomen  gradu- 
ally becoming  darker.  The  shimmering  areas  on  the  separate  seg- 
ments generally  brownish.  All  the  other  parts  are  the  same  as  in 
the  male." 

The  other  species  of  flies  found  in  houses  in  the  Eastern  United 
States  which  are  frequently  mistaken  for  the  house  or  typhoid  fly 
may  readily  be  distinguished  by  the  characters  of  the  following  key : 

a.  Apical  cell  (Rg)  of  the  wide  ^\'ing  open,  i.e.,  the  bounding  veins 
parallel  or  divergent  (fig.  100).  Their  larvae  are  flattened,  the 
intermediate  body  segments  each  fringed  with  fleshy,  more  or 
less    spinose,    processes Fannia 

b.  Male  with  the  sides  of  the  second  and  third  abdominal  seg- 
ments translucent  yellowish.  The  larva  with  three  pairs 
of  nearly  equal  spiniferous  appendages  on  each  segment, 


146  Arthropods  as  Simple  Carriers  of  Disease 

arranged  in  a  longitudinal  series  and  in  addition  two  pairs 
of  series  of  smaller  processes    (fig.    100)    F.    canicularis 
bb.  Male  with  blackish  abdomen,  middle  tibia  with  a  tubercle 
beyond  the  middle.     The  larva  with  spiniferous  appen- 
dages of  which  the  dorsal  and  ventral  series  are  short,  the 
lateral  series  long  and  feathered  (fig.  loi) .  .  .  .F.  scalaris 
aa.  Apical   cell    (R)    of    the  wing  more  or    less  narrowed  in  the 
margin;  i.  e.,  the  bounding  veins  more  or  less  converging 
(fig.  108). 
b.  The  mouth-parts  produced  and  pointed,  fitted  for  piercing. 
c.  Palpi  much  shorter  than  the  proboscis ;   a  brownish  gray 
fly,  its  thorax  with  three  rather  broad  whitish  stripes; 
on  each  border  of  the  middle  stripe  and  on  the  mesal 
borders  of  the  lateral  stripes  is  a  blackish  brown  line. 
Abdomen  yellowish  brown;    on  the  second,  third  and 
fourth  segments  are  three  brown  spots  which  may  be 
faint  or  even  absent.     The  larvse  live  in  dung.     The 

stable-fly  (fig.  no) Stomoxys  calcitrans 

cc.  Palpi  nearly  as  long  as  the  proboscis.     Smaller  species 
than  the  house-fly.     The  horn-fly  (fig.  167) 

Hcematohia  irritans 
bb.  Mouth-parts  blunt,  fitted  for  lapping. 

c.     Thorax,  particularly  on  the  sides  and  near  the  base  of  the 

wings  with  soft  golden  yellow  hairs  among  the  bristles. 

This  fly  is  often  found  in  the  house  in  very  earl}^  spring 

or  even  in  the  winter.     The  cluster-fly,  Pollenia  rudis 

cc.  Thorax  without  golden  yellow  hairs  among  the  bristles. 

d.     The  last  segment  of  the  vein  M  with  an  abrupt 

angle,     (fig.  108).     The  larvse  live  in  manure, 

etc House-fly,  Musca  domes tica 

dd.  The  last  segment  of  vein  M  with  a  broad,  gentle 

curve  (fig.  102). 

e.     Eyes  microscopically  hairy;    each  abdominal 

segment  with  two  spots.     Lar\^se  in  dung. 

Myiospila  meditabunda 

ee.  Eyes  bare;  abdomen  gray  and  brown  marbled. 

Muscina 
f .     With  black  legs  and  palpi.   M.  assimilis 


The  House-fly  as  a  Carrier  of  Disease 


147 


ff.  With  legs  more  or  less  yellowish;  palpi 
yellow.  Larvas  in  decaying  vegetable 
substances,   dung,   etc.   M.   stabulans 

It  is  almost  universally  believed  that  the  adults  of  Musca  domestica 
hibernate,  remaining  dormant  throughout  the  winter  in  attics, 
around  chimneys,  and  in  sheltered  but  cold  situations.  This  belief 
has  been  challenged  by  Skinner  (19 13),  who  maintains  that  all  the 
adult  flies  die  off  during  the  fall  and  early  winter  and  that  the  species 
is  carried  over  in  the  pupal  stage,  and  in  no  other  way.  The  cluster- 
flv,  Pollenia  nidis,  undoubtedlv  does  hibernate  in  attics  and  similar 


108.     The  house  or  typhoid  fly  (Musca  domestica  (4x)).     After  Howard. 

situations  and  is  often  mistaken  for  the  house-fly.  In  so  far  as 
concerns  Musca  domestica,  the  important  question  as  to  hibernation 
in  the  adult  stage  is  an  open  one.  Many  observations  by  one  of  the 
writers  (Johannsen)  tend  to  confirm  Dr.  Skinner's  conclusion,  in  so 
far  as  it  applies  to  conditions  in  the  latitude  of  New  York  State. 
Opposed,  is  the  fact  that  various  experimentors,  notably  Hewitt 
(19 10)  and  Jepson  (1909)  wholly  failed  to  carry  pupee  through  the 
■winter. 

The  house-fly  breeds  by  preference  in  horse  manure.  Indeed, 
Dr.  Howard,  whose  extensive  studies  of  the  species  especially  qualify 
him  for  expressing  an  opinion  on  the  subject,  has  estimated  that  under 
ordinary  city  and  town  conditions,  more  than  ninety  per  cent  of  the 
flies  present  in  houses  have  come  from  horse  stables  or  their  vicinity. 
They  are  not  limited  to  such  localities,  by  any  means,  for  it  has  been 
found  that  they  would  develop  in  almost  any  fermenting  organic 
substance.     Thus,  they  have  been  bred  from  pig,  chicken,  and  cow 


148  Arthropods  as  Simple  Carriers  oj  Disease 

manure,  dirty  waste  paper,  decaying  vegetation,  decaying  meat, 
slaughter-house  refuse,  sawdust-sweepings,  and  many  other  sources. 
A  fact  which  makes  them  especially  dangerous  as  disease-carriers 
is  that  they  breed  readily  in  human  excrement. 

The  eggs  are  pure  white,  elongate  ovoid,  somewhat  broader  at 
the  anterior  end.  They  measure  about  one  millimeter  (1-25  inch) 
in  length.  They  are  deposited  in  small,  irregtdar  clusters,  one 
hundred  and  twenty  to  one  hundred  and  fifty  from  a  single  fly.  A 
female  may  deposit  as  many  as  four  batches  in  her  life  time.  The 
eggs  hatch  in  from  eight  to  twenty -four  hours. 

The  newly  hatched  larva,  or  maggot  (fig.  108),  measures  about  two 
millimeters  (1-12  inch)  in  length.  It  is  pointed  at  the  head  end  and 
blunt  at  the  opposite  end,  where  the  spiracular  openings  are  borne. 
It  grows  rapidly,  molts  three  times  and  reaches  maturity  in  from  six 
to  seven  days,  under  favorable  conditions. 

The  pupal  stage,  like  that  of  related  flies,  is  passed  in  the  old 
larval  skin  which,  instead  of  being  molted,  becomes  contracted  and 
heavily  chitinized,  forming  the  so-called  puparium  (fig.  108).  The 
pupal  stage  may  be  completed  in  from  three  to  six  days. 

Thus  during  the  warm  summer  months  a  generation  of  flies  may 
be  produced  in  ten  to  twelve  days.  Hewitt  at  Manchester,  England, 
found  the  minimum  to  be  eight  days  but  states  that  larvae  bred  in 
the  open  air  in  horse  manure  which  had  an  average  daily  temperature 
of  22.5  C,  occupied  fourteen  to  twenty  days  in  their  development, 
according  to  the  air  temperature. 

After  emergence,  a  period  of  time  must  elapse  before  the  fly  is 
capable  of  depositing  eggs.  This  period  has  been  termed  the  pre- 
oviposition  period.  Unfortunately  we  have  few  exact  data  regarding 
this  period.  Hewdtt  found  that  the  flies  became  sexually  mature  in 
ten  to  fourteen  days  after  their  emergence  from  the  pupal  state  and 
four  days  after  copulation  they  began  to  deposit  their  eggs ;  in  other 
words  the  preoviposition  stage  was  fourteen  days  or  longer.  Griffith 
(1908)  found  this  period  to  be  ten  days.  Dr.  Howard  believes  that 
the  time  "must  surely  be  shorter,  and  perhaps  much  shorter,  under 
midsummer  conditions,  and  in  the  freedom  of  the  open  air."  He 
emphasizes  that  the  point  is  of  great  practical  importance,  since  it  is 
during  this  period  that  the  trapping  and  other  methods  of  destroying 
the  adult  flies,  will  prove  most  useful. 

Howard  estimates  that  there  may  be  nine  generations  of  flies  a 
year  under  outdoor  conditions  in  places  comparable  in  climate  to 


The  House-fly  as  a  Carrier  of  Disease  149 

Washington.  The  number  may  be  considerably  increased  in  wanner 
climates. 

The  rate  at  which  flies  may  increase  under  favorable  conditions  is 
astoimding.  Various  writers  have  given  estimates  of  the  numbers  of 
flies  which  may  develop  as  the  progeny  of  a  single  individual,  provid- 
ing all  the  eggs  and  all  the  individual  flies  survived.  Thus,  Howard 
estimates  that  from  a  single  female,  depositing  one  hundred  and 
twenty  eggs  on  April  15th,  there  may  be  by  September  loth, 
5,598,720,000,000  adults.  Fortunately,  living  forms  do  not  produce 
in  any  such  mathematical  manner  and  the  chief  value  of  the  figures 
is  to  illustrate  the  enormous  struggle  for  existence  which  is  con- 
stantly taking  place  in  nature. 

Flies  may  travel  for  a  considerable  distance  to  reach  food  and 
shelter,  though  normally  they  pass  to  dwellings  and  other  sources 
of  food  supply  in  the  immediate  neighborhood  of  their  breeding 
places.  Copeman,  Howlett  and  Merriman  (191 1)  marked  flies  by 
shaking  them  in  a  bag  containing  colored  chalk.  Such  flies  were 
repeatedly  recovered  at  distances  of  eight  to  one  thousand  yards 
and  even  at  a  distance  of  seventeen  hundred  yards,  nearly  a  mile. 

Hindle  and  Merriman  (1914)  continued  these  experiments  on  a 
large  scale  at  Cambridge,  England.  They  "do  not  think  it  likely 
that,  as  a  rule,  flies  travel  more  than  a  quarter  of  a  mile  in  thickly- 
housed  areas."  In  one  case  a  single  fly  was  recovered  at  a  distance 
of  770  yards  but  a  part  of  this  distance  was  across  open  fen-land. 
The  surprising  fact  was  brought  out  that  flies  tend  to  travel  either 
against  or  across  the  wind.  The  actual  direction  followed  may  be 
determined  either  directly  by  the  action  of  the  wind  (positive  anemo- 
tropism) ,  or  indirectly  owing  to  the  flies  being  attracted  by  any  odor 
that  it  may  convey  from  a  source  of  food.  They  conclude  that  it  is 
likely  that  the  chief  conditions  favoring  the  disposal  of  flies  are  fine 
weather  and  a  warm  temperature.  The  nature  of  the  locality  is 
another  considerable  factor.  Hodge  (19 13)  has  shown  that  when 
aided  b}'  the  wind  they  may  fly  to  much  greater  distances  over  the 
water.  He  reports  that  at  Cleveland,  Ohio,  the  cribs  of  the  water 
works,  situated  a  mile  and  a  quarter,  five  miles,  and  six  miles  out  in 
Lake  Erie  are  invaded  by  a  regular  plague  of  flies  when  the  wind 
blows  from  the  city.  Investigation  showed  that  there  was  absolutely 
nothing  of  any  kind  in  which  flies  could  breed  on  the  crib. 

The  omnivorous  habits  of  the  house-fly  are  matters  of  everyday 
obser\'ation.     From  our  view  point,  it  is  sufficient  to  emphasize 


ISO 


Arthropods  as  Simple  Carriers  of  Disease 


that  from  feeding  on  excrement,  on  sputum,  on  open  sores,  or  on 
putrifying  matter,  the  flies  may  pass  to  the  food  or  milk  upon  the  table 
or  to  healthy  mucous  membranes,  or  uncontaminated  wounds. 
There  is  nothing  in  its  appearance  to  tell  whether  the  fly  that  comes 
blithely  to  sup  with  you  is  merely  unclean,  or  whether  it  has  just 
finished  feeding  upon  dejecta  teeming  with  typhoid  bacilli. 


109.      Pulvillus  of  foot  of  house-fly,  showing  glandular  hairs. 

The  method  of  feeding  of  the  house-fly  has  an  important  bearing 
on  the  question  of  its  ability  to  transmit  pathogenic  organisms. 
Graham-Smith  (19  lo)  has  shown  that  when  feeding,  flies  frequently 
moisten  soluble  substances  with  "vomit"  which  is  regurgitated  from 
the  crop.  This  is,  of  course,  loaded  with  bacteria  from  previous 
food.  When  not  sucked  up  again  these  drops  of  liquid  dry,  and  pro- 
duce round  marks  with  an  opaque  center  and  rim  and  an  intervening 
less  opaque  area.  Fly-specks,  then,  consist  of  both  vomit  spots 
and  feces.  Graham-Smith  shows  a  photograph  of  a  cupboard  window 
where,  on  an  area  six  inches  square,  there  were  counted  eleven  hundred 
and  two  vomit  marks  and  nine  fecal  deposits. 


The  House-fly  as  a  Carrier  of  Disease  151 

From  a  bacteriologist's  viewpoint  a  discussion  of  the  possibility 
of  a  fly's  carrying  bacteria  would  seem  superfluous.  Any  exposed 
object,  animate  or  inanimate,  is  contaminated  by  bacteria  and  will 
transfer  them  if  brought  into  contact  with  suitable  culture  media, 
whether  such  substance  be  food,  or  drink,  open  wounds,  or  the  sterile 
culture  media  of  the  laboratory.  A  needle  point  may  convey  enough 
germs  to  produce  disease.  Much  more  readily  may  the  house-fly 
\vith  its  covering  of  hairs  and  its  sponge-like  pulvilli  (fig.  109)  pick 
up  and  transfer  bits  of  filth  and  other  contaminated  material. 

For  popular  instruction  this  inevitable  transfer  of  germs  by  the 
house-fly  is  strikingly  demonstrated  by  the  oft  copied  illustration 
of  the  tracks  of  a  fly  on  a  sterile  culture  plate.  Two  plates  of  gela- 
tine or,  better,  agar  medium  are  prepared.  Over  one  of  these  a  fly 
(with  wings  clipped)  is  allowed  to  walk,  the  other  is  kept  as  a  check. 
Both  are  put  aside  at  room  temperature,  to  be  examined  after  twenty- 
four  to  fort^'-eight  hours.  At  the  end  of  that  time,  the  check  plate 
is  as  clear  as  ever,  the  one  which  the  fly  has  walked  is  dotted  with 
colonies  of  bacteria  and  fungi.  The  value  in  the  experiment  consists 
in  emphasizing  that  by  this  method  we  merely  render  visible  what  is 
constantly  occurring  in  nature. 

A  comparable  experiment  which  we  use  in  our  elementary  labora- 
tory work  is  to  take  three  samples  of  dean  (preferably,  sterile)  fresh 
milk  in  sterile  bottles.  One  of  them  is  plugged  with  a  pledget  of 
cotton,  into  the  second  is  dropped  a  fly  from  the  laboratory  and  into 
the  third  is  dropped  a  fly  which  has  been  caught  feeding  upon  gar- 
bage or  other  filth.  After  a  minute  or  two  the  flies  are  remov^ed  and 
the  vials  plugged  as  was  number  one.  The  three  are  then  set  aside 
at  room  temperature.  When  examined  after  twenty-four  hours 
the  milk  in  the  first  vial  is  either  still  sweet  or  has  a  "  clean"  sour  odor; 
that  of  the  remaining  two  is  very  different,  for  it  has  a  putrid  odor, 
which  is  usually  more  pronounced  in  the  case  of  sample  number 
three. 

Several  workers  have  carried  out  experiments  to  determine  the 
number  of  bacteria  carried  by  flies  under  natural  conditions.  One 
of  the  most  extended  and  best  known  of  these  is  the  series  by  Esten 
and  Mason  (1908).  These  workers  caught  flies  from  various  sources 
in  a  sterilized  net,  placed  them  in  a  sterile  bottle  and  poured  over 
them  a  known  quantity  of  sterilized  water,  in  which  they  were  shaken 
so  as  to  wash  the  bacteria  from  their  bodies.  They  found  the  number 
of  bacteria  on  a  single  fly  to  range  from  550  to  6,600,000.     Early  in 


152  Arthropods  as  Simple  Carriers  of  Disease 

the  fly  season  the  numbers  of  bacteria  on  flies  are  comparatively 
small,  while  later  the  numbers  are  comparatively  ver}^  large.  The 
place  where  flies  live  also  determines  largel}^  the  numbers  that  the}^ 
carry.  The  lowest  number,  550,  was  from  a  fly  caught  in  the 
bacteriological  laboratory,  the  highest  number,  6,600,000  was  the 
average  from  eighteen  swill-barrel  flies.  Torrey  (19 12)  made  exami- 
nation of  "wild"  flies  from  a  tenement  house  district  of  New  York 
City.  He  found  "that  the  surface  contamination  of  these  'wild' 
flies  may  varv^  from  570  to  4,400,000  bacteria  per  insect,  and  the 
intestinal  bacterial  content  from  16,000  to  28,000,000." 

Less  well  known  in  this  country  is  the  work  of  Cox,  Lewis,  and 
Glynn  (19 12).  They  examined  over  four  hundred  and  fifty  naturally 
infected  house-flies  in  Liverpool  during  September  and  early  October. 
Instead  of  washing  the  flics  they  were  allowed  to  swim  on  the  surface 
of  sterile  water  for  flve,  fifteen,  or  thirt}'  minutes,  thus  giving  natural 
conditions,  where  infection  occurs  from  vomit  and  dejecta  of  the 
flies,  as  well  as  from  their  bodies.  They  found,  as  might  be  expected, 
that  flies  from  either  insanitary  or  congested  areas  of  the  city  contain 
far  more  bacteria  than  those  from  the  more  sanitary,  less  congested, 
or  suburban  areas.  The  number  of  aerobic  bacteria  from  the  former 
varied  from  800,000  to  500,000,000  per  fly  and  from  the  latter  from 
21,000  to  100,000.  The  number  of  intestinal  forms  conveyed  by 
flies  from  insanitary  or  congested  areas  was  from  10,000  to  333,000,000 
as  compared  with  from  100  to  10,000  carried  by  flies  from  the  more 
sanitary  areas. 

Pathogenic  bacteria  and  those  allied  to  the  food  poisoning  group 
were  only  obtained  from  the  congested  or  moderately  congested 
areas  and  not  from  the  suburban  areas,  where  the  chances  of  infesta- 
tion were  less. 

The  interesting  fact  was  brought  out  that  flies  caught  in  milk 
shops  apparently  carry  and  obtain  more  bacteria  than  those  from 
other  shops  with  exposed  food  in  a  similar  neighborhood.  The. 
writers  explained  this  as  probably  due  to  the  fact  that  milk  when 
accessible,  especially  during  the  summer  months,  is  suitable  culture 
medium  for  bacteria,  and  the  flies  first  inoculate  the  milk  and  later 
reinoculate  themselves,  and  then  more  of  the  milk,  so  establishing  a 
vicious  circle. 

They  conclude  that  in  cities  where  food  is  plentiful  flies  rarely 
migrate  from  the  locality  in  which  they  are  bred,  and  consequently 
the  number  of  bacteria  which  they  carr\^  depends  upon  the  general 


The  House-fly  as  a  Carrier  of  Disease  153 

standard  of  cleanliness  in  that  locality.  Flies  caught  in  a  street  of 
modem,  fairly  high  class,  workmen's  dwellings  forming  a  sanitary 
oasis  in  the  midst  of  a  slum  area,  carried  far  less  bacteria  than  those 
caught  in  the  adjacent  neighborhood. 

Thus,  as  the  amount  of  dirt  carried  by  flies  in  any  particular 
locality,  measured  in  the  terms  of  bacteria,  bears  a  definite  relation 
to  the  habits  of  the  people  and  to  the  state  of  the  streets,  it  demon- 
strates the  necessity  of  efficient  municipal  and  domestic  cleanliness, 
if  the  food  of  the  inhabitants  is  to  escape  pollution,  not  only  with 
harmless  but  also  \\4th  occasional  pathogenic  bacteria. 

The  above  cited  work  is  of  a  general  nature,  but,  especially  in 
recent  years,  many  attempts  have  been  made  to  determine  more 
specifically  the  abilit}^  of  flies  to  transmit  pathogenic  organisms. 
The  critical  reviews  of  Nuttall  and  Jepson  (1909),  Howard  (191 1), 
and  Graham-Smith  (19 13)  should  be  consulted  by  the  student  of 
the  subject.  We  can  only  cite  here  a  few  of  the  more  striking  experi- 
ments. 

Celli  (1888)  fed  flies  on  pure  cultures  of  Bacillus  typhostis  and  de- 
clared that  he  was  able  to  recover  these  organisms  from  the  intestinal 
contents  and  excrement. 

Firth  and  Horrocks  (1902),  cited  by  Nuttall  and  Jepson,  "kept 
Musca  domestica  (also  bluebottles)  in  a  large  box  measuring  4x3x3 
feet,  wnth  one  side  made  of  glass.  They  were  fed  on  material 
contaminated  with  cultures  of  B.  typhosus.  Agar  plates,  litmus, 
glucose  broth  and  a  sheet  of  clean  paper  were  at  the  same  time 
exposed  in  the  box.  After  a  few  days  the  plates  and  broth  were 
removed  and  incubated  with  a  positive  result."  Graham-Smith 
(19 10)  "carried  out  experiments  mth  large  numbers  of  flies  kept 
in  gauze  cages  and  fed  for  eight  hours  on  emulsions  of  B.  typhosus 
in  syrup.  After  that  time  the  infested  syrup  was  removed  and  the 
flies  were  fed  on  plain  syrup.  B.  typhosus  was  isolated  up  to  48 
hoiu-s  (but  not  later)  from  emulsions  of  their  feces  and  from  plates 
over  which  they  walked." 

Several  other  workers,  notably  Hamilton  (1903),  Ficker  (1903), 
Bertarelli  (19 10)  Faichnie  (1909),  and  Cochrane  (19 12),  have  iso- 
lated B.  typhosus  from  "wild"  flies,  naturally  infected.  The  papers 
of  Faichnie  and  of  Cochrane  we  have  not  seen,  but  they  are  quoted 
in  extenso  by  Graham-Smith  (19 13). 

On  the  whole,  the  evidence  is  conclusive  that  typhoid  germs  not 
only  may  be  accidentally  carried  on  the  bodies  of  house-flies  but 


154  Arthropods  as  Simple  Carriers  of  Disease 

may  pass  through  their  bodies  and  be  scattered  in  a  viable  condition 
in  the  feces  of  the  fly  for  at  least  two  days  after  feeding.  Similar, 
results  have  been  reached  in  experiments  with  cholera,  tuberculosis 
and  yaws,  the  last-mentioned  being  a  spirochaete  disease.  Darling 
(1913)  has  shown  that  murrina,  a  trypanosome  disease  of  horses 
and  mules  in  the  Canal  zone  is  transmitted  by  house-flies  which  feed 
upon  excoriated  patches  of  diseased  animals  and  then  pass  to  cuts 
and  galls  of  healthy  animals. 

Since  it  is  clear  that  flies  are  abundantly  able  to  disseminate 
viable  pathogenic  bacteria,  it  is  important  to  consider  whether  they 
have  access  to  such  organisms  in  nature.  A  consideration  of  the 
method  of  spread  of  typhoid  will  serve  to  illustrate  the  way  in  which 
flies  may  play  an  important  r61e. 

Typhoid  fever  is  a  specific  disease  caused  by  Bacillus  typhosus, 
and  by  it  alone.  The  causative  organism  is  to  be  found  in  the  excre- 
ment and  urine  of  patients  siifTering  from  the  disease.  More  than 
that,  it  is  often  present  in  the  dejecta  for  days,  weeks,  or  even  months 
and  years,  after  the  individual  has  recovered  from  the  disease. 
Individuals  so  infested  are  known  as  "typhoid  carriers"  and  they, 
together  with  those  suffering  from  mild  cases,  or  "walking  typhoid," 
are  a  constant  menace  to  the  health  of  the  community  in  which  they 
are  found. 

Human  excrement  is  greedily  visited  by  flies,  both  for  feeding  and 
for  ovipositing.  The  discharges  of  typhoid  patients,  or  of  chronic 
"carriers,"  when  passed  in  the  open,  in  box  privies,  or  camp  latrines, 
or  the  like,  serve  to  contaminate  myriads  of  the  insects  which  may 
then  spread  the  germ  to  human  food  and  drink.  Other  intestinal 
diseases  may  be  similarly  spread.  There  is  abundant  epidaemiologi- 
cal  evidence  that  infantile  diarrhoea,  dysentery,  and  cholera  may  be 
so  spread. 

Stiles  and  Keister  (19 13)  have  shown  that  spores  of  Lamblia 
intestinalis ,  a  flagellate  protozoan  living  in  the  human  intestine, 
may  be  carried  by  house-flies.  Though  this  species  is  not  normally 
pathogenic,  one  or  more  species  of  Entamoeba  are  the  cause  of  a  type 
of  a  highly  fatal  tropical  dysentery.  Concerning  it,  and  another 
protozoan  parasite  of  man,  they  say,  "If  flies  can  carry  Lamblia 
spores  measuring  10  to  y^ji,  and  bacteria  that  are  much  smaller,  and 
particles  of  lime  that  are  much  larger,  there  is  no  ground  to  assume 
that  flies  may  not  carry  Entamoeba  and  Trichomonas  spores. 


TJte  House-fly  as  a  Carrier  of  Disease  155 

Tuberculosis  is  one  of  the  diseases  which  it  is  quite  conceivable , 
may  be  carried  occasionally.     The  sputum  of  tubercular  patients 
is  ^•er^'  attractive  to  flies,  and  various  workers,  notably  Graham- 
Smith,  have  found  that  Musca  domestica  may  distribute  the  bacillus 
for  several  days  after  feeding  on  infected  material. 

A  type  of  purulent  opthalmia  which  is  very  prevalent  in  Egypt 
is  often  said  to  be  carried  by  flies.  Nuttall  and  Jepson  (1909) 
consider  that  the  evidence  regarding  the  spread  of  this  disease  by 
flies  is  conclusive  and  that  the  possibility  of  gonorrhoeal  secretions 
being  likeA\'ise  conveyed  cannot  be  denied. 

Many  studies  have  been  published,  shomng  a  marked  agreement 
between  the  occurrence  of  typhoid  and  other  intestinal  diseases 
and  the  prevalence  of  house-flies.  The  most  clear-cut  of  these  are 
the  studies  of  the  Army  Commission  appointed  to  investigate  the 
cause  of  epidemics  of  enteric  fever  in  the  volunteer  camps  in  the 
Southern  United  States  during  the  Spanish- American  War.  Though 
their  findings  as  presented  by  Vaughan  (1909),  have  been  quoted 
very  many  times,  they  are  so  germane  to  our  discussion  that  they 
will  bear  repetition: 

"Flies  swarmed  over  infected  fecal  matter  in  the  pits  and  fed 
upon  the  food  prepared  for  the  soldiers  in  the  mess  tents.  In  some 
instances  W'here  lime  had  recently  been  sprinkled  over  the  contents 
of  the  pits,  flies  with  their  feet  whitened  with  lime  were  seen  walking 
over  the  food."  Under  such  conditions  it  is  no  wonder  that  "These 
pests  had  inflicted  greater  loss  upon  American  soldiers  than  the  arms 
of  Spain." 

Similar  conditions  prevailed  in  South  Africa  during  the  Boer  War. 
Seamon  believes  that  very  much  of  the  success  of  the  Japanese  in 
their  fight  against  Russia  was  due  to  the  rigid  precautions  taken  to 
prevent  the  spread  of  disease  by  these  insects  and  other  means. 

Veeder  has  pointed  out  that  the  characteristics  of  a  typical  fly- 
borne  epidemic  of  typhoid  are  that  it  occurs  in  little  neighborhood 
epidemics,  extending  by  short  leaps  from  house  to  house,  without 
regard  to  water  supply  or  ami:hing  else  in  common.  It  tends  to 
follow  the  direction  of  prevailing  winds  (cf .  the  conclusions  of  Hindle 
and  Merriman).  It  occurs  during  warm  weather.  Of  course,  when 
the  epidemic  is  once  well  under  wa^^  other  factors  enter  into  its  spread. 

In  general,  flies  may  be  said  to  be  the  chief  agency  in  the  spread  of 
typhoid  in  villages  and  camps.  In  cities  with  modem  sewer  systems 
they  are  less  important,  though  even  under  the  best  of  such  condi- 


156  Arthropods  as  Simple  Carriers  of  Disease 

tions,  they  are  important  factors.  Howard  has  emphasized  that  in 
such  cities  there  are  still  many  uncared-for  box  privies  and  that,  in 
addition,  the  deposition  of  feces  overnif;;ht  in  uncared-for  waste  lots 
and  alleys  is  common. 

Not  only  unicellular  organisms,  such  as  bacteria  and  protozoa, 
but  also  the  eggs,  embryos  and  larvae  of  parasitic  worms  have  been 
found  to  be  transported  by  house-flies.  Ransom  (191 1)  has  found 
that  Habronema  musccB,  a  nematode  worm  often  found  in  adult  flies, 
is  the  immature  stage  of  a  parasite  occurring  in  the  stomach  of  the 
horse.  The  eggs  or  embryos  passing  out  with  the  feces  of  the  horse, 
are  taken  up  by  fiy  larvae  and  carried  OA^er  to  the  imago  stage. 

Grassi  (1883),  Stiles  (1889),  Calandi-uccio  (1906),  and  especially 
Nicoll  (191 1),  have  been  the  chief  investigators  of  the  ability  of 
house-flies  to  carry  the  ova  and  embryos  of  human  intestinal  parasites. 
Graham-Smith  (1913)  summarizes  the  work  along  this  line  as  follows : 

"It  is  evident  from  the  investigations  that  have  been  quoted  that 
house-flies  and  other  species  are  greatly  attracted  to  the  ova  of 
parasitic  worais  contained  in  feces  and  other  materials,  and  make 
great  efforts  to  ingest  them.  Unless  the  ova  are  too  large  they  often 
succeed,  and  the  eggs  are  deposited  uninjured  in  their  feces,  in  some 
cases  up  to  the  third  day  at  least.  The  eggs  may  also  be  carried  on 
their  legs  or  bodies.  Under  suitable  conditions,  food  and  fluids 
may  be  contaminated  with  the  eggs  of  various  parasitic  worms  by  flies, 
and  in  one  case  infection  of  the  human  subject  has  been  observed. 
Feces  containing  tape-worm  segments  may  continue  to  be  a  source  of 
infection  for  as  long  as  a  fortnight.  Up  to  the  present,  however, 
there  is  no  evidence  to  show  what  part  flies  play  in  the  dissemination 
of  parasitic  worms  under  natural  conditions." 

Enough  has  been  said  to  show  that  the  house-fly  must  be  dealt 
with  as  a  direct  menace  to  public  health.  Control  measures  are 
not  merely  matters  of  convenience  but  are  of  vital  importance. 

Under  present  conditions  the  speedy  elimination  of  the  house-fly 
is  impossible  and  the  first  thing  to  be  considered  is  methods  of  pro- 
tecting food  and  drink  from  contamination.  The  first  of  these 
method?  is  the  thorough  screening  of  doors  and  windows  to  prevent 
the  entrance  of  flies.  In  the  case  of  kitchen  doors,  the  flies,  attracted 
by  odors,  are  likely  to  swarm  onto  the  screen  and  improve  the  first 
opportunity  for  gaining  an  entrance.  This  difficulty  can  be  largely 
avoided  by  screening-in  the  back  porch  and  placing  the  screen  door 
at  one  end  rather  than  directlv  before  the  door. 


The  House-fly  as  a  Carrier  of  Disease  157 

The  use  of  sticky  fly  paper  to  catch  the  pests  that  gain  entrance 
to  the  house  is  preferable  to  the  various  poisons  often  used.  Of  the 
latter,  formalin  (40  per  cent  formaldehyde)  in  the  proportion  of  two 
tablespoonfuls  to  a  pint  of  water  is  very  efficient,  if  all  other  liquids 
are  remo\Td  or  covered,  so  that  the  flies  must  depend  on  the  formalin 
for  drink.  The  mixture  is  said  to  be  made  more  attractive  by  the 
addition  of  sugar  or  milk,  though  we  have  found  the  plain  solution 
wholly  satisfactory',  under  proper  conditions.  It  should  be  em- 
phasized that  this  formalin  mixture  is  not  perfectly  harmless,  as  so 
often  stated.  There  are  on  record  cases  of  severe  and  even  fatal 
poisoning  from  the  accidental  drinking  of  solutions. 

When  flies  are  ver}'  abundant  in  a  room  they  can  be  most  readily 
gotten  rid  of  by  fiimigation  with  sulphur,  or  by  the  use  of  pure 
pyrethrum  powder  either  burned  or  puffed  into  the  air.  Herrick 
(1913)  recommends  the  follo^\dng  method:  "At  night  all  the  doors 
and  ^^^ndows  of  the  kitchen  should  be  closed;  fresh  powder  should 
be  sprinkled  over  the  stove,  on  the  window  ledges,  tables,  and  in  the 
air.  In  the  morning  flies  will  be  found  lying  around  dead  or  stupified. 
They  may  then  be  swept  up  and  burned."  This  method  has  proved 
very  efficaceous  in  some  of  the  large  dining  halls  in  Ithaca. 

The  writers  have  had  little  success  in  fumigating  with  the  vapors 
of  carbolic  acid,  or  carbolic  acid  and  gum  camphor,  although  these 
methods  %\-ill  aid  in  driving  flies  from  a  darkened  room. 

All  of  these  methods  are  but  makeshifts.  As  Howard  has  so  well 
put  it,  "the  truest  and  simplest  way  of  attacking  the  fl}^  problem 
is  to  prevent  them  from  breeding,  by  the  treatment  or  abolition  of 
all  places  in  which  they  can  breed.  To  permit  them  to  breed  un- 
disturbed and  in  countless  numbers,  and  to  devote  all  our  energy  to 
the  problem  of  keeping  them  out  of  our  dwellings,  or  to  destroy  them 
after  they  have  once  entered  in  spite  of  all  obstacles,  seems  the 
wrong  way  to  go  about  it." 

We  have  already  seen  that  Musca  domestica  breeds  in  almost  any 
fermenting  organic  material.  While  it  prefers  horse  manure,  it 
breeds  also  in  human  feces,  cow  dung  and  that  of  other  animals, 
and  in  refuse  of  many  kinds.  To  efficiently  combat  the  insect, 
these  breeding  places  must  be  removed  or  must  be  treated  in  some 
such  way  as  to  render  them  tmsuitable  for  the  development  of  the 
larv£e.  Under  some  conditions  individual  work  may  prove  effective, 
but  to  be  tnily  efficient  there  must  be  extensive  and  thorough  co- 
operative efforts. 


158  Arthropods  as  Simple  Carriers  of  Disease 

Manvire,  garbage,  and  the  like  should  be  stored  in  tight  receptacles 
and  carted  away  at  least  once  a  week.  The  manure  may  be  carted 
to  the  fields  and  spread.  Even  in  spread  manure  the  larvae  may  con- 
tinue their  development.  Howard  points  out  that  "it  often  happens 
that  after  a  lawTi  has  been  heavily  manured  in  early  summer  the 
occupants  of  the  house  will  be  pestered  with  flies  for  a  time,  but 
finding  no  available  breeding  place  these  disappear  sooner  or  later. 
Another  generation  will  not  breed  in  the  spread  manure." 

Hutchinson  (1914)  has  emphasized  that  the  larvae  of  house- 
flies  have  deeply  engrained  the  habit  of  migrating  in  the  prepupal 
stage  and  has  shown  that  this  offers  an  important  point  of  attack 
in  attempts  to  control  the  pest.  He  has  suggested  that  maggot 
traps  might  be  developed  into  an  efficient  weapon  in  the  warfare 
against  the  house-fly.  Certain  it  is  that  the  habit  greatly  simplifies  the 
problem  of  treating  the  manure  for  the  purpose  of  killing  the  larvae. 

There  have  been  many  attempts  to  find  some  cheap  chemical 
which  would  destroy  fly  larvae  in  horse  manure  without  injuring  the 
bacteria  or  reducing  the  fertilizing  values  of  the  manure.  The  litera- 
ture aboiinds  in  recommendations  of  kerosene,  lime,  chloride  of  lime, 
iron  sulphate,  and  other  substances,  but  none  of  them  have  met  the 
situation.  The  whole  question  has  been  gone  into  thoroughly  by 
Cook,  Hutchinson  and  Scales  (19 14),  who  tested  practically  all  of  the 
substances  which  have  been  recommended.  They  find  that  by  far 
the  most  effective,  economical,  and  practical  of  the  substances  is 
borax  in  the  commercial  form  in  which  it  is  available  throughout  the 
country. 

"Borax  increases  the  water-soluble  nitrogen,  ammonia  and  alkali- 
nity of  manure  and  apparently  does  not  permanently  injure  the 
bacterial  fiora.  The  application  of  manure  treated  with  borax  at  the 
rate  of  0.62  pound  per  eight  bushels  (10  cubic  feet)  to  soil  does  not 
injure  the  plants  thus  far  tested,  although  its  cumulative  effect,  if 
any,  has  not  been  determined." 

As  their  results  clearly  show  that  the  substances  so  often  recom- 
mended are  inferior  to  borax,  we  shall  quote  in  detail  their  directions 
for  treating  manure  so  as  to  kill  fly  eggs  and  maggots. 

"Apply  0.62  pound  borax  or  0.75  pound  calcined  colemanite  to 
every  10  cubic  feet  (8  bushels)  of  manure  immediately  on  its  removal 
from  the  bam.  Apply  the  borax  particularly  around  the  outer 
edges  of  the  pile  with  a  flour  sifter  or  any  fine  sieve,  and  sprinkle  two 
•or  three  gallons  of  water  over  the  borax-treated  manure. 


The  House-fly  as  a  Carrier  oj  Disease  159 

"The  reason  for  applying  the  borax  to  the  fresh  manure  immedi- 
ately after  its  removal  from  the  stable  is  that  the  flies  lay  their  eggs 
on  the  fresh  manure,  and  borax,  when  it  comes  in  contact  with  the 
eggs,  prevents  their  hatching.  As  the  maggots  congregate  at  the 
outer  edge  of  the  pile,  most  of  the  borax  should  be  applied  there. 
The  treatment  should  be  repeated  with  each  addition  of  fresh  manure, 
but  when  the  manure  is  kept  in  closed  boxes,  less  frequent  applica- 
tions will  be  sufficient.  When  the  calcined  colemanite  is  available, 
it  may  be  used  at  the  rate  of  0.75  pound  per  10  cubic  feet  of  manure, 
and  is  a  cheaper  means  of  killing  the  maggots.  In  addition  to  the 
application  of  borax  to  horse  manure  to  kill  fly  larvae,  it  may  be 
applied  in  the  same  proportion  to  other  manures,  as  well  as  to  refuse 
and  garbage.  Borax  may  also  be  applied  to  the  floors  and  crevices  in 
bams,  stables,  markets,  etc.,  as  well  as  to  street  sweepings,  and  water 
should  be  added  as  in  the  treatment  of  horse  manure.  After  estimat- 
ing the  amount  of  material  to  be  treated  and  weighing  the  necessar^^ 
amount  of  borax,  a  measure  may  be  used  which  will  hold  the  proper 
amount,  thus  avoiding  the  subsequent  weighings. 

"While  it  can  be  safely  stated  that  no  injurious  action  will  follow 
the  application  of  manure  treated  with  borax  at  the  rate  of  0.62 
pound  for  eight  bushels,  or  even  larger  amounts  in  the  case  of  some 
plants,  nevertheless  the  borax-treated  manure  has  not  been  studied 
in  connection  with  the  growth  of  all  crops,  nor  has  its  cumulative 
effect  been  determined.  It  is  therefore  recommended  that  not  more 
than  1 5  tons  per  acre  of  the  borax-treated  manure  should  be  applied 
to  the  field.  As  truckmen  use  considerably  more  than  this  amount, 
it  is  suggested  that  all  cars  containing  borax-treated  manure  be  so 
marked,  and  that  public-health  officials  stipulate  in  their  directions 
for  this  treatment  that  not  over  0.62  pound  for  eight  bushels  of  manure 
be  used,  as  it  has  been  shown  that  larger  amounts  of  borax  will 
injure  most  plants.  It  is  also  recommended  that  all  public-health 
officials  and  others,  in  recommending  the  borax  treatment  for  kill- 
ing fly  eggs  and  maggots  in  manure,  warn  the  public  against  the 
injurious  effects  of  large  amounts  of  borax  on  the  growth  of  plants." 

"The  amount  of  manure  from  a  horse  varies  with  the  straw  or 
other  bedding  used,  but  12  or  15  bushels  per  week  represent  the 
approximate  amount  obtained.  As  borax  costs  from  five  to  six 
cents  per  pound  in  100-pound  lots  in  Washington,  it  will  make  the 
cost  of  the  borax  practically  one  cent  per  horse,  per  day.  And  if 
calcined  colemanite  is  purchased  in  large  shipments  the  cost  should 
be  considerably  less." 


i6o  Arthropods  as  Simple  Carriers  of  Disease 

Hodge  (19 lo)  has  approached  the  problem  of  fly  extermination 
from  another  viewpoint.  He  believes  that  it  is  practical  to  trap 
flies  out  of  doors  during  the  preoviposition  period,  when  they  are 
sexually  immature,  and  to  destroy  such  numbers  of  them  that  the 
comparatively  few  which  survive  will  not  be  able  to  lay  eggs  in  suffi- 
cent  numbers  to  make  the  next  generation  a  nuisance.  To  the  end 
of  capturing  them  in  enormous  numbers  he  has  devised  traps  to  be 
fitted  over  garbage  cans,  into  stable  windows,  and  connected  with  the 
kitchen  window  screens.  Under  some  conditions  this  method  of 
attack  has  proved  very  satisfactory. 

One  of  the  most  important  measures  for  preventing  the  spread 
of  disease  by  flies  is  the  abolition  of  the  common  box  privy.  In 
villages  and  rural  districts  this  is  today  almost  the  only  type  to  be 
found.  It  is  the  chief  factor  in  the  spread  of  typhoid  and  other 
intestinal  diseases,  as  well  as  intestinal  parasites.  Open  and  ex- 
posed to  myriads  of  flies  which  not  only  breed  there  but  which  feed 
upon  the  excrement,  they  furnish  ideal  conditions  for  spreading  con- 
tamination. Even  where  efforts  are  made  to  cover  the  contents 
with  dust,  or  ashes,  or  lime,  flies  may  continue  to  breed  unchecked. 
Stiles  and  Gardner  have  shown  that  house-flies  buried  in  a  screened 
stand-pipe  forty-eight  inches  under  sterile  sand  came  to  the  surface. 
Other  flies  of  undetermined  species  struggled  up  through  seventy- 
two  inches  of  sand. 

So  great  is  the  menace  of  the  ordinary  box  privy  that  a  number  of 
inexpensive  and  simple  sanitary  privies  have  been  designed  for  use 
where  there  are  not  modem  sewer  systems.  Stiles  and  Lumsden 
(191 1)  have  given  minute  directions  for  the  construction  of  one  of  the 
best  types,  and  their  bulletin  should  be  obtained  by  those  interested. 

Another  precaution  which  is  of  fundamental  importance  in 
preventing  the  spread  of  typhoid,  is  that  of  disinfecting  all  discharges 
from  patients  suffering  with  the  disease.  For  this  purpose,  quick- 
lime is  the  cheapest  and  is  wholly  satisfactory.  In  chamber  vessels 
it  should  be  used  in  a  quantity  equal  to  that  of  the  discharge  to  be 
treated.  It  should  be  allowed  to  act  for  two  hours.  Air-slaked 
lime  is  of  no  value  whatever.  Chloride  of  lime,  carbolic  acid,  or 
formalin  may  be  used,  but  are  more  expensive.  Other  intestinal 
diseases  demand  similar  precautions. 

Stomoxys  calcitrans,  the  stable-fly — It  is  a  popular  belief  that 
house-flies  bite  more  viciously  just  before  a  rain.     As  a  matter  of 


Stomoxys  calcitrans,  the  Siable-fly 


i6i 


fact,  the  true  house-flies  never  bite,  for  their  mouth-parts  are  not 
fitted  for  piercing.  The  basis  of  the  misconception  is  the  fact  that  a 
true  biting  fly,  Stomoxys  calcitrans  (fig.  no),  closely  resembling  the 
house-fly,  is  frequently  found  in  houses  and  may  be  driven  in  in 
greater  numbers  by  muggy  weather.  From  its  usual  habitat  this 
fly  is  known  as  the  "stable-flv"  or,  sometimes  as  the  "biting  house- 
fly." 

Stomoxys  calcitrans  may  be  separated  from  the  house-fly  by  the  use 
of  the  key  on  p.  145.     It  may  be  more  fully  characterized  as  follows: 

The  eyes  of  the  male  are  separated  by  a  distance  equal  to  one- 
fourth  of  the  diameter  of  the  head,  in  the  female  by  one-third.     The 


110.     stomoxys  calcitrans;  adult,  larva,  puparium  and  details,  (xs).      After  Howard. 

frontal  stripe  is  black,  the  cheeks  and  margins  of  the  orbits  silvery- 
white.  The  antennae  are  black,  the  arista  feathered  on  the  upper 
side  only.  The  proboscis  is  black,  slender,  fitted  for  piercing  and 
projects  forward  in  front  of  the  head.  The  thorax  is  grayish,  marked 
by  four  conspicuous,  more  or  less  complete  black  longitudinal  stripes; 
the  scutellum  is  paler;  the  macrochaetas  are  black.  The  abdomen  is 
gray,  dorsally  with  three  brown  spots  on  the  second  and  third  seg- 
ments and  a  median  spot  on  the  fourth.  These  spots  are  more 
pronounced  in  the  female..  The  legs  are  black,  the  pul villi  distinct. 
The  wings  are  hyaline,  the  vein  M1  +  2  less  sharply  curved  than  in 
the  house-fly,  the  apical  cell  being  thus  more  widely  open  (cf.  fig. 
no).     Length  7  mm. 

This  fly  is  widely  distributed,  being  found  the  world  over.     It  was 
probably  introduced  into  the  United  States,  but  has  spread  to  all 


i62  Arthropods  as  Simple  Carriers  of  Disease 

parts  of  the  country.  Bishopp  (19 13)  regards  it  as  of  much  more 
importance  as  a  pest  of  domestic  animals  in  the  grain  belt  than  else- 
where in  the  United  States.  The  life-history  and  habits  of  this 
species  have  assumed  a  new  significance  since  it  has  been  suggested 
that  it  may  transmit  the  human  diseases,  infantile  paralysis  and 
pellagra.  In  this  country,  the  most  detailed  study  of  the  fly  is  that 
of  Bishopp  (19 13)  whose  data  regarding  the  life  cycle  are  as  follows: 

The  eggs  like  those  of  the  house-fly,  are  about  one  mm. 
in  length.  Under  a  magnifying  glass  they  show  a  distinct  furrow 
along  one  side.  When  placed  on  any  moist  substance  they  hatch 
in  from  one  to  three  days  after  being  deposited. 

The  larvae  or  maggots  (fig.  no)  have  the  typical  shape  and  actions 
of  most  maggots  of  the  Muscid  group.  They  can  be  distinguished 
from  those  of  the  house-fly  as  the  stigma-plates  are  smaller,  much 
further  apart,  with  the  slits  less  sinuous.  Development  takes  place 
fairly  rapidly  when  the  proper  food  conditions  are  available  and 
the  growth  is  completed  within  eleven  to  thirty  or  more  days. 

The  pupa  (fig.  no),  like  that  of  related  flies,  undergoes  its  develop- 
ment within  the  contracted  and  hardened  last  larval  skin,  or  pu- 
parium.  This  is  elongate  oval,  slightly  thicker  towards  the  head  end, 
and  one-sixth  to  one-fourth  of  an  inch  in  length.  The  pupal  stage 
requires  six  to  twenty  days,  or  in  cool  weather  considerably  longer. 

The  life-cycle  of  the  stable-fly  is  therefore  considerably  longer 
than  that  of  Musca  domestica.  Bishopp  found  that  complete 
development  might  be  undergone  in  nineteen  days,  but  that  the 
average  period  was  somewhat  longer,  ranging  from  twenty-one  to 
twenty-five  days,  where  conditions  are  very  favorable.  The  longest 
period  which  he  observed  was  forty-three  days,  though  his  finding 
of  full  grown  larvse  and  pupae  in  straw  during  the  latter  part  of 
March,  in  Northern  Texas,  showed  that  development  may  require 
about  three  months,  as  he  considered  that  these  stages  almost  cer- 
tainly developed  from  eggs  deposited  the  previous  December. 

The  favorite  breeding  place,  where  available,  seems  to  be  straw  or 
manure  mixed  with  straw.  It  also  breeds  in  great  numbers  in  horse- 
manure,  in  company  with  Musca  domestica. 

Newstead  considers  that  in  England  the  stable-fly  hibernates  in 
the  pupal  stage.  Bishopp  finds  that  in  the  southern  part  of  the 
United  States  there  is  no  true  hibernation,  as  the  adults  have  been 
foimd  to  emerge  at  various  times  during  the  winter.  He  believes 
that  in  the  northern  United  States  the  winter  is  normally  passed 


Other  Arthropods  as  Simple  Carriers  163 

in  the  larval  and  pupal  stages,  and  that  the  adults  which  have  been 
observ'ed  in  heated  stables  in  the  dead  of  winter  were  bred  out  in 
refuse  \\'ithin  the  warm  bams  and  were  not  hibernating  adiilts. 

Graham-Smith  (1913)  states  that  although  the  stable-fly  fre- 
quents stable  manure,  it  is  probably  not  an  important  agent  in 
distributing  the  organisms  of  intestinal  diseases.  Bishopp  makes  the 
important  observation  that  "it  has  never  been  found  breeding  in 
human  excrement  and  does  not  frequent  malodorous  places,  which 
are  so  attractive  to  the  house-fly.  Hence  it  is  much  less  likely  to 
carry  t\TDhoid  and  other  germs  which  may  be  found  in  such  places." 

Questions  of  the  possible  agency  of  Stomoxys  calcitrans  in  the  trans- 
mission of  infantile  paralysis  and  of  pellagra,  we  shall  consider  later. 

Other  arthropods  which  may  serve  as  simple  carriers  of  patho- 
genic organisms — It  should  be  again  emphasized  that  any  insect  which 
has  access  to,  and  comes  in  contact  with,  pathogenic  organisms 
and  then  passes  to  the  food,  or  drink,  or  the  body  of  man,  may  serve 
as  a  simple  carrier  of  disease.  In  addition  to  the  more  obvious 
illustrations,  an  interesting  one  is  the  pre\'iously  cited  case  of  the 
transfer  of  Dermatobia  cyaniventris  by  a  mosquito  (fig.  81-84). 
Darling  (19 13)  has  shown  that  in  the  tropics,  the  omnipresent  ants 
may  be  important  factors  in  the  spread  of  disease. 


CHAPTER  VI 
ARTHROPODS  AS  DIRECT  INOCULATORS  OF  DISEASE  GERMS 

We  have  seen  that  any  insect  which,  like  the  house-fly,  has  access 
to  disease  germs  and  then  comes  into  contact  ■with,  the  food  or  drink 
of  man,  may  serve  to  disseminate  disease.  Moreover,  it  has  been 
clearly  established  that  a  contaminated  insect,  alighting  upon 
wounded  or  abraded  surfaces,  may  infect  them.  These  are  instances 
of  mere  accidental,  mechanical  transfer  of  pathogenic  organisms. 

Closely  related  are  the  instances  of  direct  inoculation  of  disease 
germs  by  insects  and  other  arthropods.  In  this  type,  a  blood- 
sucking species  not  only  takes  up  the  germs  but,  passing  to  a  healthy 
individual,  it  inserts  its  contaminated  mouth-parts  and  thus  directly 
inoculates  its  victim.  In  other  words,  the  disease  is  transferred 
just  as  blood  poisoning  maA^  be  induced  by  the  prick  of  a  contami- 
nated needle,  or  as  the  laboratory  worker  ma}^  inoculate  an  experi- 
mental animal. 

Former  1}^  it  was  supposed  that  this  method  of  the  transfer  of 
disease  by  arthropods  was  a  ver>^  common  one  and  many  instances 
are  cited  in  the  earlier  literature  of  the  subject.  It  is,  howe^■er, 
difficult  to  draw  a  sharp  line  between  such  cases  and  those  in  which, 
on  the  one  hand,  the  arthropod  ser\^es  as  a  mere  passive  carrier  or, 
on  the  other  hand,  serves  as  an  essential  host  of  the  pathogenic 
organism.  More  critical  study  of  the  subject  has  led  to  the  belief 
that  the  importance  of  the  r61e  of  arthropods  as  direct  inoculators 
has  been  much  overestimated. 

The  principal  reason  for  regarding  this  phase  of  the  subject  as 
relatively  unimportant,  is  derived  from  a  study  of  the  habits  of  the 
blood-sucking  species.  It  is  found  that,  in  general,  they  are  inter- 
mittent feeders,  visiting  their  hosts  at  inter\'als  and  then  abstaining 
from  feeding  for  a  more  or  less  extended  period,  while  digesting  their 
meal.  In  the  meantime,  most  species  of  bacteria  or  of  protozoan 
parasites  with  which  they  might  have  contaminated  their  mouth- 
parts,  would  have  perished,  through  inability  to  %vithstand  drying. 

In  spite  of  this,  it  must  be  recognized  that  this  method  of  transfer 
does  occur  and  must  be  reckoned  with  in  an}^  consideration  of  the 
relations  of  insects  to  disease.  We  shall  first  cite  some  general 
illustrations  and  shall  then  discuss  the  role  of  fleas  in  the  spreading 
of  bubonic  plague,  an  illustration  which  cannot  be  regarded  as  t\'pi- 
cal,  since  it  involves  more  than  mere  passive  carriage. 


Some  Illustrations  of  Direct  Inoculation  165 

Some  Illustrations  of  Direct  Inoculation  of  Disease  Germs 

BY  Arthropods 

In  discussing  poisonous  arthropods,  we  have  already  emphasized 
that  species  which  are  of  themselves  innocuous  to  man,  may  occasion- 
alh'  introduce  bacteria  by  their  bite  or  sting  and  thus  cause  more  or 
less  severe  secondan,'  symptoms.  That  such  cases  should  occur,  is 
no  more  than  is  to  be  expected.  The  mouth-parts  or  the  sting  of 
the  insect  are  not  sterile  and  the  chances  of  their  carrying  pyogenic 
organisms  are  always  present. 

A  lore  strictly  falling  in  the  category  of  transmission  of  disease 
germs  by  direct  inoculation  are  the  instances  where  the  insect,  or 
related  form,  feeds  upon  a  diseased  animal  and  passes  promptly  to  a 
health}^  indi^4dual  which  it  infects.  Of  such  a  nature  are  the  follow- 
ing: 

\'arious  species  of  biting  flies  are  factors  in  the  dissemination  of 
anthrax,  an  infectious  and  usually  fatal  disease  of  animals  and, 
occasionally,  of  man.  That  the  bacteria  with  which  the  blood  of 
diseased  animals  teem  shortly  before  death  might  be  transmitted 
b\"  such  insects  has  long  been  contended,  but  the  evidence  in  support 
of  the  view  has  been  imsatisfactory.  Recently,  Mitzmain  (19 14) 
has  reported  a  series  of  experiments  which  show  conclusively  that  the 
disease  may  be  so  conveyed  by  a  horse-fly,  Tahanus  striatus,  and  by 
the  stable-fly,  Stomoxys  calcitrans. 

Mitzmain's  experiments  were  tried  ^\'ith  an  artificially  infected 
guinea  pig,  which  died  of  the  disease  upon  the  third  day.  The  flies 
were  applied  two  and  one-half  hours,  to  a  few  minutes,  before  the 
death  of  the  animal.  With  both  species  the  infection  was  success- 
fully transferred  to  healthy  guinea  pigs  by  the  direct  method,  in 
which  the  flies  were  interrupted  while  feeding  on  the  sick  animal. 
The  evidence  at  hand  does  not  warrant  the  conclusion  that  insect 
transmission  is  the  rule  in  the  case  of  this  disease. 

The  nagana,  or  tsetse-fly  disease  of  cattle  is  the  most  virulent 
disease  of  domestic  animals  in  certain  parts  of  Africa.  It  is  caused 
by  a  protozoan  blood  parasite,  Trypanosoma  hrucei,  which  is  con- 
veyed to  healthy  animals  by  the  bite  of  Glossina  morsitans  and  possi- 
bly other  species  of  tsetse-flies.  The  flies  remain  infective  for 
forty -eight  hours  after  feeding  on  a  diseased  animal.  The  insect 
also  serves  as  an  essential  host  of  the  parasite. 

Surra,  a  similar  trypanosomiasis  affecting  especially  horses  and 
mules,  occurs  in  southern  Asia,  IMalaysia,  and  the  Philippines  where 


1 66  Arthropods  as  Direct  Inoculators  of  Disease  Germs 

the  tsetse-flies  are  not  to  be  found.  It  is  thought  to  be  spread  by- 
various  species  of  blood-sucking  flies  belonging  to  the  genera  Stomoxys, 
Hmnatohia,  and  Tabanus.  Mitzmain  (19 13)  demonstrated  that  in 
the  Philippines  it  is  conveyed  mechanically  by  Tabanus  striatus. 

The  sleeping  sickness  of  man,  in  Africa,  has  also  been  supposed 
to  be  directly  inoculated  by  one,  or  several,  species  of  tsetse-flies. 
It  is  now  known  that  the  fly  may  convey  the  disease  for  a  short 
time  after  feeding,  but  that  there  is  then  a  latent  period  of  from 
fourteen  to  twenty-one  days,  after  which  it  again  becomes  infectious. 
This  indicates  that  in  the  meantime  the  parasite  has  been  under- 
going some  phase  of  its  life-cycle  and  that  the  fly  serves  as  an  inter- 
mediate host.  We  shall  therefore  consider  it  more  fully  under  that 
grouping. 

These  are  a  few  of  the  cases  of  direct  inoculation  which  may  be 
cited  as  of  the  simpler  type.  We  shall  next  consider  the  rdle  of  the 
flea  in  the  dissemination  of  the  bubonic  plague,  an  illustration 
complicated  by  the  fact  that  the  bacillus  multiples  within  the  insect 
and  may  be  indirectly  inoculated. 

The  Role  of   Fleas    in    the    Transmission    of  the    Plague 

The  plague  is  a  specific  infectious  disease  caused  by  Bacillus  pestis. 
It  occurs  in  several  forms,  of  which  the  bubonic  and  the  pneumonic 
are  the  most  common.  According  to  Wyman,  80  per  cent  of  the 
human  cases  are  of  the  bubonic  type.  It  is  a  disease  which,  under 
the  name  of  oriental  plague,  the  pest,  or  the  black  death,  has  ravaged 
almost  from  time  immemorial  the  countries  of  Africa,  Asia,  and 
Europe.  The  record  of  its  ravages  are  almost  beyond  belief.  In  542 
A.  D.  it  caused  in  one  day  ten  thousand  deaths  in  Constantinople. 
In  the  14th  century  it  was  introduced  from  the  East  and  prevailed 
throughout  Armenia,  Asia  Minor,  Egypt  and  Northern  Africa  and 
Europe.  Hecker  estimates  that  one-fourth  of  the  population  of 
Europe,  or  twenty-five  million  persons,  died  in  the  epidemic  of  that 
century.  From  then  imtil  the  17th  century  it  was  almost  constantly 
present  in  Europe,  the  great  plague  of  London,  in  1665  killing  68,596 
out  of  a  population  of  460,000.  Such  an  epidemic  would  mean  for 
New  York  City  a  proportionate  loss  of  over  600,000  in  a  single  year. 
It  is  little  wonder  that  in  the  face  of  such  an  appalling  disaster  sus- 
picion and  credulity  were  rife  and  the  wildest  demoralization  ensued. 

During  the  14th  century  the  Jews  were  regarded  as  responsible 
for  the  disease,  through  poisoning  wells,  and  were  subjected  to  the 


Role  of  Fleas  in  the  Transuiissioti  of  Plas^ue 


167 


111.     A  contemporaneous  engraving  of  the  pest  hospital  in  Vienna  in  1679. 
After  Peters. 


most  incredible  persecution  and  torture.  In  Milan  the  \dsitation 
of  1630  was  credited  to  the  so-called  anointers, — men  who  were 
supposed  to  spread  the  plague  by  anointing  the  walls  vnth.  magic 
ointment — and  the  most  horrible  tortures  that  human  ingenuity 
could  devise  were  imposed  on  scores  of  \dctims,  regardless  of  rank 
or  of  public  service  (fig.  112, a).  Manzoni's  great  historical  novel, 
"The  Betrothed"  has  well  pictured  conditions  in  Italy  during  this 
period. 

In  modem  times  the  plague  is  confined  primarily  to  warm  climates, 
a  condition  which  has  been  brought  about  largely  through  general 
improvement  in  sanitary  conditions. 

At  present,  the  hotbed  of  the  disease  is  India,  where  there  were 
1,040,429  deaths  in  1904  and  where  in  a  period  of  fifteen  years, 
ending  with  January  191 2,  there  were  over  15,000,000  deaths.  The 
reported  deaths  in  that  country  for  1913  totaled  198,875. 

During  the  winter  of  1910-11  there  occurred  in  Manchuria  and 
North  China  a  virulent  epidemic  of  the  pneumonic  plague  which 
caused  the  death  of  nearly  50,000  people.  The  question  as  to  its 
origin  and  means  of  spread  will  be  especially  referred  to  later. 

Until  recent  years,  the  plague  had  not  been  known  to  occur  in 
the  New  World  but  there  were  outbreaks  in  Brazil  and  Hawaii  in 
1899,  and  in  1900  there  occurred  the  first  cases  in  San   Francisco. 


i68 


Arthropods  as  Direct  Inoculators  of  Disease  Germs 


u 
^  O 

.2  o 


3  o 

a  C 


Role  of  Fleas  in  the  Transmission  of  Plague 


169 


In  California  there  were  125  cases  in  the  period  1900-04;  three  cases 
in  the  next  three  years  and  then  from  May  1907  to  March  1908, 
during  the  height  of  the  outbreak,  170  cases.  Since  that  time  there 
have  been  only  sporadic  cases,  the  last  case  reported  being  in  May 
19 14.  Still  more  recent  were  the  outbreaks  in  the  Philippine  Islands, 
Porto  Rico,  and  Cuba. 

On  June  24,  19 14,  there  was  recognized  a  case  of  human  plague 
in  New  Orleans.  The  Federal  Health  Service  immediately  took 
charge,  and  measures  for  the  eradication  of  the  disease  were  vigor- 
ously enforced.  Up  to  Otcober  10,  19 14  there  had  been  reported 
30  cases  of  the  disease  in  man,  and  iSi  cases  of  plague  in  rats. 


IHP 


112  b.     The  modern  method  of  combating  the  plague.      A  day's  catch  of  rats  in  the  fight 
against  plague  in  San  Francisco.     Courtesy  of  Review  of  Reviews. 

The  present-day  methods  of  combating  bubonic  plague  are  well 
illustrated  by  the  fight  in  San  Francisco.  Had  it  not  been  for  the 
strenuous  and  radical  anti-plague  campaign  directed  by  the  United 
States  Marine  Hospital  Service  we  might  have  had  in  our  own 
country  an  illustration  of  what  the  disease  can  accomplish.  On  what 
newly  acquired  knowledge  was  this  fight  based  ? 

The  basis  was  laid  in  1894,  when  the  plague  bacillus  was  first 
discovered.  All  through  the  centuries,  before  and  during  the  Christian 
era,  down  to  1894,  the  subject  was  enveloped  in  darkness  and  there 
had  been  a  helpless,  almost  hopeless  struggle  in  ignorance  on  the  part 
of  physicians,  sanitarians,  and  public  health  officials  against  the 
ravages  of  this  dread  disease.  Now  its  cause,  method  of  propaga- 
tion and  means  to  prevent  its  spread  are  matters  of  scientific  cer- 
tainty. 


170  Arthropods  as  Direct  Inoculators  of  Disease  Germs 

After  the  discovery  of  the  causative  organism,  one  of  the  first 
advances  was  the  estabHshment  of  the  identity  of  human  plague 
and  that  of  rodents.  It  had  often  been  noted  that  epidemics  of  the 
human  disease  were  preceded  by  great  epizootics  among  rats  and 
mice.  So  well  established  was  this  fact  that  with  the  Chinese, 
unusual  mortality  among  these  rodents  was  regarded  as  foretelling 
a  visitation  of  the  human  disease.  That  there  was  more  than  an 
accidental  connection  between  the  two  was  obvious  when  Yersin, 
the  discoverer  of  Bacillus  ^^5/z5,  announced  that  during  an  epidemic 
the  rats  found  dead  in  the  houses  and  in  the  streets  almost  always 
contain  the  bacillus  in  great  abundance  in  their  organs,  and  that  many 
of  them  exhibit  veritable  buboes. 

Once  it  was  established  that  the  diseases  were  identical,  the  atten- 
tion of  the  investigators  was  directed  to  a  study  of  the  relations 
between  that  of  rats  and  of  humans,  and  evidence  accumulated  to 
show  that  the  bubonic  plague  was  primarily  a  disease  of  rodents 
and  that  in  some  manner  it  was  conveyed  from  them  to  man. 

There  yet  remained  unexplained  the  method  of  transfer  from  rat 
to  man.  As  long  ago  as  the  i6th  century,  Mercuralis  suggested 
that  house-flies  were  guilty  of  disseminating  the  plague  but  modem 
investigation,  while  blaming  the  fly  for  much  in  the  way  of  spreading 
disease,  show  that  it  is  an  insignificant  factor  in  this  case. 

Search  for  blood-sucking  insects  which  would  feed  on  both  rodents 
and  man,  and  which  might  therefore  be  implicated,  indicated  that 
the  fleas  most  nearly  met  the  conditions.  At  first  it  was  urged  that 
rat  fleas  would  not  feed  upon  man  and  that  the  fleas  ordinarily  attack- 
ing man  would  not  feed  upon  rats.  More  critical  study  of  the  habits 
of  fleas  soon  showed  that  these  objections  were  not  well-founded. 
Especially  important  was  the  evidence  that  soon  after  the  death  of 
their  host,  rat  fleas  deserted  its  body  and  might  then  become  a  pest 
in  houses  where  they  had  not  been  noticed  before. 

Attention  was  directed  to  the  fact  that  while  feeding,  fleas  are  in 
the  habit  of  squirting  blood  from  the  anus  and  that  in  the  case  of  those 
which  had  fed  upon  rats  and  mice  dying  of  the  plague,  virulent  plague 
bacilli  were  to  be  found  in  such  blood.  Liston  (1905)  even  found,, 
and  subsequent  investigations  confirmed,  that  the  plague  bacilli 
multiply  in  the  stomach  of  the  insect  and  that  thus  the  blood  ejected 
was  richer  in  the  organisms  than  was  that  of  the  diseased  animal. 
It  was  found  that  a  film  of  this  infected  blood  spread  out  under  the 
body  of  the  flea  and  that  thus  the  bacilli  might  be  inoculated  by  the 
bite  of  the  insect  and  by  scratching. 


Role  of  Fleas  in  the  Transmission  of  Plague  171 

Very  recently,  Bacot  and  Martin  (1914)  have  paid  especial 
attention  to  the  question  of  the  mechanism  of  the  transmission  of 
the  plague  bacilli  by  fleas.  They  believe  that  plague  infested  fleas 
regurgitate  blood  through  the  mouth,  and  that  under  conditions 
precluding  the  possibility  of  infection  by  dejecta,  the  disease  may  be 
thus  transmitted.  The  evidence  does  not  seem  sufficient  to  establish 
that  this  is  the  chief  method  of  transmission. 

Conclusive  experimental  proof  that  fleas  transmit  the  disease  is 
further  available  from  a  number  of  sources.  The  most  extensive 
series  of  experiments  is  that  of  the  English  Plague  Commission  in 
India,  which  reported  in  1906  that: 

On  thirty  occasions  a  healthy  rat  contracted  plague  in  sequence 
of  living  in  the  neighborhood  of  a  plague  infected  rat  under  cir- 
cumstances which  prevented  the  healthy  rat  coming  in  contact  with 
either  the  body  or  excreta  of  the  diseased  animal. 

In  twenty-one  experiments  out  of  thirty-eight,  healthy  rats  living 
in  flea-proof  cages  contracted  plague  when  exposed  to  rat  fleas 
{Xenopsylla  cheopis),  collected  from  rats  dead  or  dying  of  septicaemic 
plague. 

Close  contact  of  plague-infected  with  healthy  animals,  if  fleas 
are  excluded,  does  not  give  rise  to  an  epizootic  among  the  latter. 
As  the  huts  were  never  cleaned  out,  close  contact  included  contact 
with  feces  and  urine  of  infected  animals,  and  contact  with,  and  eat- 
ing of  food  contaminated  with  feces  and  urine  of  infected  animals, 
as  well  as  pus  from  open  plague  ulcers.  Close  contact  of  young, 
even  when  suckled  by  plague-infected  mothers,  did  not  give  the 
disease  to  the  former. 

If  fleas  are  present,  then  the  epizootic,  once  started,  spreads  from 
animal  to  animal,  the  rate  of  progress  being  in  direct  proportion  to 
the  number  of  fleas. 

Aerial  infection  was  excluded.  Thus  guinea-pigs  suspended  in  a 
cage  two  feet  above  the  ground  did  not  contract  the  disease,  while 
in  the  same  hut  those  animals  allowed  to  run  about  and  those  placed 
two  inches  above  the  floor  became  infected.  It  had  previously 
been  found  that  a  rat  flea  could  not  hop  farther  than  about  five 
inches. 

Guinea  pigs  and  monkeys  were  placed  in  plague  houses  in  pairs, 
both  protected  from  soil  contact  infection  and  both  equally  exposed 
to  aerial  infection,  but  one  surrounded  with  a  layer  of  tangle-foot 
paper  and  the  other  surrounded  with  a  layer  of  sand.  The  follow- 
ing observations  were  made: 


172  Arthropods  as  Direct  Inoculators  of  Disease  Germs 

(a)  Many  fleas  were  caught  in  the  tangle-foot,  a  certain  pro- 
portion of  which  were  found  on  dissection  to  contain  in  their  stomachs 
abundant  bacilli  microscopically  identical  with  plague  bacilli.  Out 
of  eighty-five  human  fleas  dissected  only  one  contained  these  bacilli, 
while  out  of  seventy-seven  rat  fleas  twenty-three  were  found  thus 
infected. 

(6)  The  animals  surrounded  with  tangle-foot  in  no  instance 
developed  plague,  while  several  (24  per  cent)  of  the  non-protected 
animals  died  of  the  disease. 

Thus,  the  experimental  evidence  that  fleas  transmit  the  plague 
from  rat  to  rat,  from  rats  to  guinea  pigs,  and  from  rats  to  monkeys 
is  indisputable.  There  is  lacking  direct  experimental  proof  of  its 
transfer  from  rodents  to  man  but  the  whole  chain  of  indirect  evi- 
dence is  so  complete  that  there  can  be  no  doubt  that  such  a  transfer 
does  occur  so  commonly  that  in  the  case  of  bubonic  plague  it  must 
be  regarded  as  the  normal  method. 

Rats  are  not  the  only  animals  naturally  attacked  by  the  plague 
but  as  already  suggested,  it  occurs  in  various  other  rodents.  In 
California  the  disease  has  spread  from  rats  to  ground  squirrels 
(Otospermophilus  heecheyi),  a  condition  readily  arising  from  the 
frequency  of  association  of  rats  with  the  squirrels  in  the  neighbor- 
hood of  tow^ns,  and  from  the  fact  that  the  two  species  of  fleas  found 
on  them  are  also  found  on  rats.  While  the  danger  of  the  disease 
being  conveyed  from  squirrels  to  man  is  comparatively  slight,  the 
menace  in  the  situation  is  that  the  squirrels  may  become  a  more  or 
less  permanent  reser\'oir  of  the  disease  and  infect  rats,  which  may 
come  into  more  frequent  contact  with  man. 

The  tarbagan  {Arctomys  bobac),  is  a  rodent  found  in  North  Man- 
churia, which  is  much  prized  for  its  fur.  It  is  claimed  that  this  ani- 
mal is  extremely  susceptible  to  the  plague  and  there  is  evidence  to 
indicate  that  it  was  the  primary  source  of  the  great  outbreak  of 
pneumonic  plague  which  occurred  in  Manchuria  and  North  China 
during  the  winter  of  1910-11. 

Of  fleas,  any  species  which  attacks  both  rodents  and  man  may  be 
an  agent  in  the  transmission  of  the  plague.  We  have  seen  that  in 
India  the  species  most  commonly  implicated  is  the  rat  flea,  Xenopsylla 
cheopis,  (=  Lcemopsylla  or  Pulex  cheopis)  (fig.  89).  This  species  has 
also  been  found  commonly  on  rats  in  San  Francisco.  The  cat  flea, 
Cienocephalus  felts,  the  dog  flea,  Ctenocephalus  cams,  the  human  flea, 
Pulex  irriians,  the  rat  fleas,  Ceratophyllus  fasciatus  and  Ctenopsyllus 
mtisculi  have  all  been  shown  to  meet  the  conditions. 


Role  of  Fleas  in  the  Transmission  of  Plague  173 

But,  however  clear  the  evidence  that  fleas  are  the  most  important 
agent  in  the  transfer  of  plague,  it  is  a  mistake  fraught  with  danger 
to  assume  that  they  are  the  only  factor  in  the  spread  of  the  disease. 
The  causative  organism  is  a  bacillus  and  is  not  dependent  upon  any 
insect  for  the  completion  of  its  development. 

Therefore,  any  blood-sucking  insect  which  feeds  upon  a  plague 
infected  man  or  animal  and  then  passes  to  a  healthy  individual, 
conceivably  might  transfer  the  bacilli.  Verjbitski  (1908)  has  shown 
experimentally  that  bed-bugs  may  thus  conve}'  the  disease.  Hertzog 
found  the  bacilli  in  a  head-louse,  Pediculus  humanus,  taken  from  a 
child  which  had  died  from  the  plague,  and  McCoy  found  them  in  a 
louse  taken  from  a  plague-infected  squirrel.  On  account  of  their 
stationar}^  habits,  the  latter  insects  could  be  of  little  significance  in 
spreading  the  disease. 

Contaminated  food  may  also  be  a  source  of  danger.  While  this 
source,  formerly  supposed  to  be  the  principal  one,  is  now  regarded  as 
unimportant,  there  is  abundant  experimental  CA^dence  to  show  that 
it  cannot  be  disregarded.  It  is  believed  that  infection  in  this  way 
can  occur  only  when  there  is  some  lesion  in  the  alimentary  canal.      | 

Still  more  important  is  the  proof  that  in  pneumonic  plague  the 
patient  is  directly  infecti\'e  and  that  the  disease  is  spread  from  man 
to  man  without  any  intermediary.  Especially  conclusive  is  the 
e\^dence  obtained  by  Drs.  Strong  and  Teague  during  the  Manchurian 
epidemic  of  1910-11.  They  found  that  during  coughing,  in  pneu- 
monic plague  cases,  even  when  sputum  visible  to  the  naked  eye  is 
not  expelled,  plague  bacilli  in  large  numbers  may  become  widely 
disseminated  into  the  surrounding  air.  By  exposing  sterile  plates 
before  patients  who  coughed  a  single  time,  very  numerous  colonies 
of  the  baccilus  were  obtained. 

But  the  great  advance  which  has  been  made  rests  on  the  dis- 
covery that  bubonic  plague  is  in  the  vast  majority  of  cases  transmitted 
by  the  flea.  The  pneumonic  type  forms  a  very  small  percentage 
of  the  human  cases  and  even  with  it,  the  evidence  indicates  that  the 
original  infection  is  derived  from  a  rodent  through  the  intermediary 
of  the  insect. 

So  modern  prophylactic  measures  are  directed  primarily  against 
the  rat  and  fleas.  Ships  coming  from  infected  ports  are  no  longer 
disinfected  for  the  purpose  of  killing  the  plague  germs,  but  are  fumi- 
gated to  destroy  the  rats  and  the  fleas  which  they  might  harbor. 
When  anchored  at  infected  ports,   ships  must  obser^^e  strenuous 


174  Arthropods  as  Direct  Inoculators  of  Disease  Germs 

precautions  to  prevent  the  ingress  of  rats.  Cargo  must  be  inspected 
just  before  being  brought  on  board,  in  order  to  insure  its  freedom  from 
rats.  Even  Hnes  and  hawsers  must  be  protected  by  large  metal  discs 
or  funnels,  for  rats  readily  run  along  a  rope  to  reach  the  ship.  Once 
infested,  the  ship  must  be  thoroughly  fumigated,  not  only  to  avoid 
carrying  the  disease  to  other  ports  but  to  obviate  an  outbreak  on 
board. 

When  an  epidemic  begins,  rats  must  be  destroyed  by  trapping 
and  poisoning.  Various  so-called  biological  poisons  have  not  proved 
practicable.  Sources  of  food  supply  should  be  cut  off  by  thorough 
cleaning  up,  by  use  of  rat-proof  garbage  cans  and  similar  measures. 
Hand  in  hand  with  these,  must  go  the  destruction  of  breeding  places, 
and  the  rat -proofing  of  dwellings,  stables,  markets,  warehouses,  docks 
and  sewers.  All  these  measiu-es  are  expensive,  and  a  few  years  ago 
would  have  been  thought  wholly  impossible  to  put  into  practice 
but  now  they  are  being  enforced  on  a  large  scale  in  every  fight  against 
the  disease. 

Rats  and  other  rodents  are  regularly  caught  in  the  danger  zone 
and  examined  for  evidence  of  infection,  for  the  sequence  of  the  epi- 
zootic and  of  the  human  disease  is  now  understood.  In  London,  rats 
are  regularly  trapped  and  poisoned  in  the  vicinity  of  the  principal 
docks,  to  guard  against  the  introduction  of  infected  animals  in  ship- 
ping. During  the  past  six  years  infected  rats  have  been  found 
yearly,  thirteen  having  been  found  in  1912.  In  Seattle,  Washington, 
seven  infected  rats  were  found  along  the  water  front  in  October,  19 13, 
and  infected  ground  squirrels  are  still  being  found  in  connection  with 
the  anti-plague  measures  in  California, 

The  procedure  during  an  outbreak  of  the  human  plague  was  well 
illustrated  by  the  fight  in  San  Francisco.  The  city  was  districted, 
and  captured  rats,  after  being  dipped  in  some  fluid  to  destroy  the  fleas, 
were  carefully  tagged  to  indicate  their  source,  and  were  sent  to  the 
laboratory  for  examination.  If  an  infected  rat  was  found,  the  officers 
in  charge  of  the  work  in  the  district  involved  were  immediately 
notified  by  telephone,  and  the  infected  building  was  subjected  to  a 
thorough  fimiigation.  In  addition,  special  attention  was  given  to 
all  the  territory  in  the  four  contiguous  blocks. 

By  measures  such  as  these,  this  dread  scourge  of  the  human  race 
is  being  brought  under  control.  Incidentally,  the  enormous  losses 
due  to  the  direct  ravages  of  rats  are  being  obviated  and  this  alone 
would  justify  the  expenditure  many  times  over  of  the  money  and 
labor  involved  in  the  anti-rat  measures. 


CHAPTER  VII 


ARTHROPODS  AS  ESSENTIAL  HOSTS   OF  PATHOGENIC  ORGANISMS 

We  now  have  to  consider  the  cases  in  which  the  arthropod  acts 
as  the  essential  host  of  a  pathogenic  organism.  In  other  words, 
cases  in  which  the  organism,  instead  of  being  passively  carried  or 
merely  accidentally  inoculated  by  the  bite  of  its  carrier,  or  vector,  is 
taken  up  and  undergoes  an  essential  part  of  its  development  within 
the  arthropod. 

In  some  cases,  the  sexual  cycle  of  the  parasite  is  undergone  in  the 
arthropod,  which  then  serves  as  the  definitive  or 
primary  host.  In  other  cases,  it  is  the  asexual  stage 
of  the  parasite  which  is  undergone,  and  the  arthropod 
then  acts  as  the  intermediate  host.  This  distinction 
is  often  overlooked  and  all  the  cases  incorrectly 
referred  to  as  those  in  which  the  insect  or  other 
arthropod  acts  as  intermediate  host. 

We  have  already  emphasized  that  this  is  the  most 
important  way  in  which  insects  may  transmit  disease, 
for  without  them  the  particiilar  organisms  concerned 
could  never  complete  their  development.  Exter- 
minate the  arthropod  host  and  the  life  cycle  of  the 
parasite  is  broken,  the  disease  is  exterminated. 

As  the  phenomenon  of  alternation  of  generations, 
as  exhibited  by  many  of  the  parasitic  protozoa,  is  a 
complicated  one  and  usually  new  to  the  student,  we 
shall  first  take  up  some  of  the  grosser  cases  illustrated 
by  certain  parasitic  worms.  There  is  the  additional 
reason  that  these  were  the  first  cases  known  of  arthro- 
pod transmission  of  pathogenic  organisms. 


113.  Dipylidium 
caninum.  The 
double  pored 
tapeworm  of  the 


Insects  as  Intermediate  Hosts   of  Tapeworms 

A  number  of  tapeworms  are  known  to  undergo  their  sexual  stage 
in  an  insect  or  other  arthropod.  Of  these  at  least  two  are  occasional 
parasites  of  man. 

Dipylidium  caninum  (figs.  113  and  114),  more  generally  known  as 
Taenia  cucumerina  or  T.  elliptica,  is  the  commonest  intestinal  parasite 
of  pet  dogs  and  cats.  It  is  occasionally  found  as  a  human  parasite, 
70  per  cent  of  the  cases  reported  being  in  young  children. 

175 


176      Arthropods  as  Essential  Hosts  of  Pathogenic  Organisms 


114.  Dipylidium  caninum. 
Rostrum  evaginated  and 
invaginated.  After 
Blanchard. 


In  1869,  Melnikoff  found  in  a  dog  louse,  Trichodectes  canis,  some 
peculiar  bodies  which  Leuckart  identified  as  the  larval  form  of  this 
tapeworm.  The  worm  is,  however,  much  more 
common  in  dogs  and  cats  than  is  the  skin  para- 
site, and  hence  it  appears  that  the  Trichodectes 
could  not  be  the  only  intermediate  host.  In 
1888,  Grassi  found  that  it  could  also  develop 
in  the  cat  and  dog  fleas,  Ctenocephahis  felis 
and  C.  canis,  and  in  the  human  flea,  Ptdex 
irritans. 

The  eggs,  scattered  among  the  hairs  of  the 
dog  or  cat,  are  ingested  by  the  insect  host  and 
in  its  body  cavity  they  develop  into  pyriform 
bodies,  about  3oo[x  in  length,  almost  entirely  destitute  of  a  bladder, 
but  in  the  immature  stage  provided  with  a  caudal  appendage  (fig.  115). 
Within  the  pear-shaped  body  (fig.  116)  are  the  invaginated  head  and 
suckers  of  the  future  tapeworm.  This  larval 
form  is  known  as  a  cysticercoid,  in  contradis- 
tinction to  the  bladder-like  cysticercus  of  many 
other  cestodes.  It  is  often  referred  to  in  liter- 
ature as  Cryptocystis  trichodectis  Villot. 

As  many  as  fifty  of  the  cysticercoids  have 
been  found  in  the  body  cavity  of  a  single  flea. 
When  the  dog  takes  up  an  infested  flea  or  louse, 
by  biting  itself,  or  when  the  cat  licks  them  up,  the 
larvae  quickly  develop  into  tapeworms,  reaching  sexual  maturity  in 
about  twenty  days  in  the  intestine  of  their  host.  Puppies  and 
kittens  are  quickly  infested  when  suckling  a  flea-infested  mother,  the 
developing  worms  having  been  found  in  the  intestines  of  puppies  not 
more  than  five  or  six  days  old. 

Infestation  of    human    beings    occurs   only 
through  accidental  ingestion  of  an  infested  flea. 
It  is  natural  that  such  cases  should  occur  largely 
in  children,  where  they  may   come   about   in 
some  such  way  as  illustrated  in  the  accompany- 
ing figures  117  and  118. 
Hymenolepis  diminuta,   very  commonly   living  in   the  intestine 
of  mice  and  rats,  is  also  known  to  occur  in  man.     Its  cysticercoid 
develops  in  the  body  cavity  of  a  surprising  range  of  meal-infesting 
insects.  Grassi  and  Rovelli  (abstract  in  Ransom,  1904)  found  it  in  the 


115.  Dipylidium  caninum- 
Immature  cystict-rcoid- 
After  Grassi  and  Rovelli. 


116, 


Dipylidium  caninum. 
Cysticercoid.  After 
ViUet. 


Insects  as  Intermediate  Hosts  of  Tapeworms 


177 


larvae  and  adult  of  a  moth,  Asopiafarinalts,  in  the  earwig,  Anisolabis 

annulipes,  the  Tenebrionid  beetles  Akis  spinosa  and  Scaurus  striatiis. 

Grassi  considers  that  the  lepi- 
dopter  is  the  normal  inter- 
mediate host.  The  insect  takes 
up  the  eggs  scattered  by  rats 
and  mice.  It  has  been  experi- 
mentally demonstrated  that 
man  may  develop  the  tape- 
worm by  swallowing  infested 
insects.  Natural  infection 
probably  occurs  by  ingesting 
such  insects  with  cereals,  or 
imperfectly  cooked  foods. 
Hymenolepis  lanceolata,  a  parasite  of  geese  and  ducks,  has  been 

reported  once  for  man.     The  supposed  cysticercoid  occurs  in  various 

small  crustaceans  of  the  family  Cyclopidse. 


117. 


One  way  in   which   Dipylidium  infection  in 
children  may  occur.     After  Blanchard. 


118.     The  probable  method  by  which  DipyHdium  infection  usually  occurs. 


178      Arthropods  as  Essential  Hosts  of  Pathogenic  Organisms 

Several  other  cestode  parasites  of  domestic  animals  are  believed 
to  develop  their  intermediate  stage  in  certain  arthropods.  Among 
these  may  be  mentioned : 

Choanotcenia  infundibulformis,  of  chickens,  developing  in  the  house- 
fly (Grassi  and  Rovelli) ; 

Davainea  cesticillus,  of  chickens,  in  some  lepidopter  or  coleopter 
(Grassi  and  Rovelli) ; 

Hymenolepis  anatina,  H.  gracilis,  H.  sinuosa,  H.  coronula  and 
Fimbriaria  fasciolaris,  all  occurring  in  ducks,  have  been  reported  as 
developing  in  small  aquatic  crustaceans.  In  these  cases,  cysticer- 
coids  have  been  found  which,  on  account  of  superficial  characters, 
have  been  regarded  as  belonging  to  the  several  species,  but  direct 
experimental  evidence  is  scant. 

Arthropods   as    Intermediate    Hosts   of     Nematode    Worms 

Filariasis  and  Mosquitoes — ^A  number  of  species  of  Nematode 
worms  belonging  to  the  genus  Filaria,  infest  man  and  other  verte- 
brates and  in  the  larval  condition  are  to  be  found  in  the  blood. 
Such  infestation  is  known  as  filariasis.  The  sexually  mature  worms 
are  to  be  found  in  the  blood,  the  lymphatics,  the  mesentery  and  sub- 
cutaneous connective  tissue.  In  the  cases  best  studied  it  has  been 
found  that  the  larval  forms  are  taken  up  by  mosquitoes  and  undergo 
a  transformation  before  they  can  attain  maturity  in  man. 

The  larv£e  circulating  in  the  blood  are  conveniently  designated 
as  microfilariae.  In  this  stage  they  are  harmless  and  only  one  species, 
Filaria  bancrofti,  appears  to  be  of  any  great  pathological  significance 
at  any  stage. 

Filaria  bancrofti  in  its  adult  state,  lives  in  the  lymphatics  of  man. 
Though  often  causing  no  injury  it  has  been  clearly  established  that 
they  and  their  eggs  may  cause  various  disorders  due  to  stoppage 
of  the  lymphatic  trunks  (fig.  119).  Manson  lists  among  other  effects, 
abscess,  varicose  groin  glands,  lymph  scrotum,  chyluria,  and  ele- 
phantiasis. 

The  geographical  distribution  of  this  parasite  is  usually  given  as 
coextensive  with  that  of  elephantiasis,  but  it  is  by  no  means  certain 
that  it  is  the  only  cause  of  this  disease  and  so  actual  findings  of  the 
parasites  are  necessary.  Manson  reports  that  it  is  "an  indigenous 
parasite  in  almost  every  country  throughout  the  tropical  and  sub- 
tropical world,  as  far  north  as  Spain  in  Europe  and  Charlestown  in 


Filariasis  and  Mosquitoes 


179 


the  United  States,  and  as  far  south  as  Brisbane  in  Australia."  In 
some  sections,  fully  50  per  cent  of  the  natives  are  infested.  Labredo 
(1910)  found  17.82  per  cent  infestation  in  Havana. 

The  lar\'al  forms  of  Filaria  hancrofti  were  first  discovered  in  1863, 
by  Demarquay,  in  a  case  of  chylous  dropsy.  They  were  subse- 
quently noted  under  similar  conditions,  by  several  workers,  and  by 
Wucherer  in  the  urine  of  twenty-eight  cases  of  tropical  chyluria, 
but  in  1872  Lewis  found  that  the  blood  of  man  was  the  normal 
habitat,  and  gave  them  the  name  Filaria  sanguinis  hominis.     The 

adult  worm  was  found  in  1876 
by  Bancroft,  and  in  1877, 
Cobboldgave  it  the  name  Fi/an'a 
hancrofti.  It  has  since  been 
found  repeatedly  in  various  parts 
of  the  lymphatic  system,  and  its 
life-history  has  been  the  subject 
of  detailed  studies  by  Manson 
(1884),  Bancroft  (1899),  Low 
(1900),  Grassi  and  Noe  (1900), 
Noe(i9oi)andFiillebom(i9io). 
The  larvae,  as  they  exist  in 
the  circulating  blood,  exhibit  a 
very  active  wriggling  movement, 
without  material  progression. 
They  may  exist  in  enormous 
niimbers,  as  many  as  five  or 
six  hundred  swarming  in  a 
single  drop  of  blood.  This  is  the  more  surprising  when  we  con- 
sider that  they  measure  about  3oo[x  x  8|x,  that  is,  their  width  is 
equal  to  the  diameter  of  the  red  blood  corpuscle  of  their  host  and 
their  length  over  thirty-seven  times  as  great. 

Their  organs  are  very  immature  and  the  structure  obscure.  When 
they  have  quieted  down  somewhat  in  a  preparation  it  may  be  seen 
that  at  the  head  end  there  is  a  six-lipped  and  very  delicate  prepuce, 
enclosing  a  short  "fang"  which  may  be  suddenly  exserted  and 
retracted.  Completely  enclosing  the  larva  is  a  delicate  sheath, 
which  is  considerably  longer  than  the  worm  itself.  To  enter  into 
further  details  of  anatomy  is  beyond  the  scope  of  this  discussion 
and  readers  interested  are  referred  to  the  work  of  Manson  and  of 
Fiillebom. 


Elephantiasis  in  Man.     From  "New 
Sydenham  Society's  Atlas." 


i8o      Arthropods  as  Essential  Hosts  of  Pathogenic  Organisms 

One  of  the  most  surprising  features  of  the  habits  of  these  larvae 
is  the  periodicity  which  they  exhibit  in  their  occurrence  in  the  peri- 
pheral blood.  If  a  preparation  be  made  during  the  day  time  there 
may  be  no  evidence  whatever  of  filarial  infestation,  whereas  a  prep- 
aration from  the  same  patient  taken  late  in  the  evening  or  during 
the  night  may  be  hterally  swarming  with  the  parasites.  Manson 
quotes  Mackenzie  as  having  brought  out  the  further  interesting 
fact  that  should  a  "filarial  subject  be  made  to  sleep  during  the  day 
and  remain  awake  at  night,  the  periodicity  is  reversed;  that  is  to  say, 
the  parasites  come  into  the  blood  during  the  day  and  disappear  from 
it  during  the  night."  There  have  been  numerous  attempts  to  explain 
this  peculiar  phenomenon  of  periodicity  but  in  spite  of  objections 
which  have  been  raised,  the  most  plausible  remains  that  of  Manson, 
who  believes  that  it  is  an  adaptation  correlated  with  the  life-habits 
of  the  liberating  agent  of  the  parasite,  the  mosquito. 

The  next  stages  in  the  development  of  Filaria  nocturna  occur  in 
mosquitoes,  a  fact  suggested  almost  simultaneously  by  Bancroft 
and  Manson  in  1877,  and  first  demonstrated  by  the  latter  very  soon 
thereafter.  The  experiments  were  first  carried  out  with  Culex 
quinquefasciaius  (=  fatigans)  as  a  host,  but  it  is  now  known  that  a 
number  of  species  of  mosquitoes,  both  anopheline  and  culicine,  may 
serve  equally  well. 

When  the  blood  of  an  infested  individual  is  sucked  up  and  reaches 
the  stomach  of  such  a  mosquito,  the  larva,  by  very  active  movements, 
escape  from  their  sheaths  and  within  a  very  few  hours  actively  mi- 
grate to  the  body  cavity  of  their  new  host  and  settle  down  primarily 
in  the  thoracic  muscles.  There  in  the  course  of  sixteen  to  twenty 
days  they  undergo  a  metamorphosis  of  which  the  more  conspicuous 
features  are  the  formation  of  a  mouth,  an  alimentary'  canal  and  a 
trilobed  tail.  At  the  same  time  there  is  an  enormous  increase  in 
size,  the  larvae  which  measured  .3  mm.  in  the  blood  becoming  1.5  mm. 
in  length.  This  developmental  period  may  be  somewhat  shortened 
in  some  cases  and  on  the  other  hand  may  be  considerably  extended. 
The  controlling  factor  seems  to  be  the  one  of  temperature. 

The  transformed  larvae  then  reenter  the  body  cavity  and  finally 
the  majority  of  them  reach  the  interior  of  the  labium  (fig.  120).  A 
few  enter  the  legs  and  antennae,  and  the  abdomen,  but  these  are 
wanderers  which,  it  is  possible,  may  likewise  ultimately  reach  the 
labium,  where  they  await  the  opportunity  to  enter  their  hrmian  host. 


Filariasis  and  Mosquitoes  i8i 

It  was  formerly  supposed  that  when  the  infested  mosquito  punc- 
tured the  skin  of  man,  the  mature  larvse  were  injected  into  the  cir- 
culation. The  manner  in  which  this  occurred  was  not  obvious,  for 
when  the  insect  feeds  it  inserts  only  the  stylets,  the  labium  itself 
remaining  on  the  surface  of  the  skin.  Fiillebom  has  cleared  up  the 
question  by  showing  that  at  this  time  the  filariae  escape  and,  like 
the  hookworm,  actively  bore  into  the  skin  of  their  new  host. 

Once  entered,  they  migrate  to  the  lymphatics  and  there  quickly 
become  sexually  mature.  The  full  grown  females  measure  85-90  mm. 
in  length  by  .2 4-. 2 8  mm.  in  diameter,  while  the  males  are  less  than 


120.     Filaria  in  the  muscles  and  labium  of  Culex.     After  Blanchard. 


half  this  size,  being  about  40  mm.  by  .1  mm.  Fecundation  occurs 
and  the  females  will  be  found  filled  with  eggs  in  various  stages  of 
development,  for  they  are  normally  viviparous. 

Filaria  philippinensis  is  reported  by  Ashbum  and  Craig  (1907)  as 
a  common  blood  filaria  in  the  Philippine  Islands.  As  they  describe 
it,  it  differs  from  Filaria  bancrofti  primarily  in  that  it  does  not  exhibit 
periodicity.  Its  development  has  been  found  to  occur  in  Culex 
quinquefasciatus,  where  it  undergoes  metamorphosis  in  about  fourteen 
or  fifteen  days.  There  is  doubt  as  to  the  species  being  distinct  from 
bancrofti. 

Several  other  species  occur  in  man  and  are  thought  to  be  trans- 
ferred by  various  insects,  among  which  have  been  mentioned  Taba- 
nidse  and  tsetse-flies,  but  there  is  no  experimental  proof  in  support 
of  such  conjectures. 


i82      Arthropods  as  Essential  Hosts  of  Pathogenic  Organisms 


Filaria  immitis  is  a  dangerous  parasite  of  the  dog,  the  adult  worm 
living  in  the  heart  and  veins  of  this  animal.  It  is  one  of  the  species 
which  has  been  clearly  shown  to  imdergo  its  development  in  the 
mosquito,  particularly  in  Anopheles  maculipennis  and  Aedes  calopus 
(=  Stegomyia).  The  larval  form  occurs  in  the  peripheral  .blood, 
especially  at  night.  When  taken  up  by  mosquitoes  they  differ  from 
Filaria  bancrofti  in  that  they  undergo  their  development  in  the 
Malpighian  tubules  rather  than  in  the  thoracic  muscles.  In 
about  twelve  days  they  have  completed  their  growth  in  the  tubules, 
pierce  the  distal  end,  and  pass  to  the  labium.  This  species  occurs 
primarily  in  China  and  Japan,  but  is  also  found  in  Europe  and  in  the 
United  States.  It  is  an  especially  favorable  species  for  studying 
the  transformations  in  the  mosquito. 

FilaricB  are  also  commonly  found  in  birds,  and  in  this  country 
this  is  the  most  available  source  of  laboratory  material.  We  have 
found  them  locally  (Ithaca,  N.  Y.)  in  the  blood  of 
over  sixty  per  cent  of  all  the  crows  examined,  at 
any  season  of  the  year,  and  have  also  found  them 
in  English  sparrows. 

In  the  crows,  they  often  occur  in  enormous 
numbers,  as  many  as  two  thousand  having  been 
found  in  a  single  drop  of  the  blood  of  the  most 
heavily  infested  specimen  examined.  For  study,  a 
small  drop  of  blood  should  be  mounted  on  a  clean 
slide  and  the  coverglass  rung  with  vaseline  or  oil 
to  prevent  evaporation.  In  this  way  they  can 
be  kept  for  hours. 

Permanent  preparations  may  be  made  by 
spreading  out  the  blood  in  a  film  on  a  perfectly 
clean  slide  and  staining.  This  is  easiest  done  by  touching  the  fresh 
drop  of  blood  with  the  end  of  a  second  slide  which  is  then  held  at 
an  angle  of  about  45°  to  the  first  slide  and  drawn  over  it  without 
pressure.  Allow  the  smear  to  dry  in  the  air  and  stain  in  the  usual 
way  with  hccmatoxylin. 


121.     Dracunculus 
medinensis;  female; 
mouth;    embryo. 
After  Bastian  and 
Leuckart. 


Other  Nematode  Parasites  of  Man  and  Animals  Developing 

IN  Arthropods 

Dracunculus  medinensis  (fig.  121),  the  so-called  guinea- worm,  is 
a  nematode  parasite  of  man  which  is  widely  distributed  in  tropical 
Africa,  Asia,  certain  parts  of  Brazil  and  is  occasionally  imported 
into  North  America. 


Other  Nematodes  Developing  in  Arthropods  183 

The  female  worm  is  excessively  long  and  slender,  measuring  nearly 
three  feet  in  length  and  not  more  than  one-fifteenth  of  an  inch  in 
diameter.  It  is  found  in  the  subcutaneous  connective  tissue  and  when 
mature  usually  migrates  to  some  part  of  the  leg. 
Here  it  pierces  the  skin  and  there  is  formed  a  small 
superficial  ulcer  through  which  the  larvae  reach  the 
exterior  after  bursting  the  body  of  the  mother. 

Fedtschenko  (1879)  found  that  when  these  larva; 
reach  the  water  they  penetrate  the  carapace  of  the 
little  crustacean,  Cyclops  (fig.  122).  Here  they  molt 
several  times  and  undergo  a  metamorphosis.  Fedts- 
chenko, in  Turkestan,  found  that  these  stages  required 
about  five  weeks,  while  Manson  who  confirmed  these 
general  results,  foimd  that  eight  or  nine  weeks  were  intermed?ate^°host*of 
required  in  the  cooler  climate  of  Engand.  Diacuncuius. 

Infection  of  the  vertebrate  host  probably  occurs  through  swallow- 
ing infested  cyclops  in  drinking  water.  Fedtschenko  was  unable  to 
demonstrate  this  experimentally  and  objection  has  been  raised  against 
the  theory,  but  Leiper  (1907),  and  Strassen  (1907)  succeeded  in  infest- 
ing monke}'s  by  feeding  them  on  cyclops  containing  the  lar\"as. 

Habronema  niuscce  is  a  worm  which  has  long  been  known  in  its 
larval  stage,  as  a  parasite  of  the  house-fly.  Carter  found  them  in 
33  per  cent  of  the  house-flies  examined  in  Bombay  during  July,  i860, 
and  since  that  time  they  have  been  shown  to  be  very  widely  distrib- 
uted. Italian  workers  reported  them  in  12  per  cent  to  30  per  cent 
of  the  flies  examined.  Hewitt  reported  finding  it  rarely  in  England. 
In  this  coimtry  it  was  first  reported  by  Leidy  who  found  it  in  about 
20  per  cent  of  the  flies  examined  at  Philadelphia,  Pa.  Since  then  it 
has  been  reported  by  several  American  w^orkers.  We  have  found  it 
at  Ithaca,  N.  Y.,  but  have  not  made  sufficient  examinations  to  justify 
stating  percentage.  Ransom  (19 13)  reports  it  in  thirty -nine  out  of 
one  hiindred  and  thirty-seven  flies,  or  28  per  cent. 

Until  very  recently  the  life-history  of  this  parasite  was  unknown 
but  the  thorough  work  of  Ransom  (1911,  1913)  has  shown  clearly 
that  the  adult  stage  occurs  in  the  stomach  of  horses.  The  embryos, 
produced  by  the  parent  worms  in  the  stomach  of  the  horse,  pass 
out  wdth  the  feces  and  enter  the  bodies  of  fly  lar\^as  which  are  develop- 
ing in  the  manure.  In  these  they  reach  their  final  stage  of  larval 
development  at  about  the  time  the  adult  flies  emerge  from  the  pupal 
stage.     In  the  adiilt  fly  they  are  commonly  found  in  the  head. 


:84      Arthropods  as  Essential  Hosts  oj  Pathogenic  Organisms 


123.     An  Echinorhynchid,  showing  the  spinose  retractile  proboscis. 


124.     June  beetle  (Lachnosterna). 


frequently  in  the  proboscis,  but  they  occur  also  in  the  thorax  and 
abdomen.  Infested  flies  are  accidentally  swallowed  by  horses  and 
the  parasite  completes  its  development  to  maturity  in  the  stomach  of 
its  definitive  host. 


Other  Nematodes  developing  in  Arthropods  185 

Gigantorhynchus  hirudinaceus  {  =  Echinorhynchus  gigas)  is  a  com- 
mon parasite  of  the  pig  and  has  been  reported  as  occurring  in  man. 
The  adult  female  is  20-35  cm.  long  and  4-9  mm.  in  diameter. 
It  lacks  an  alimentary  canal  and  is  provided  with  a  strongly  spined 
protractile  rostrum,  by  means  of  which  it  attaches  to  the  intestinal 
mucosa  of  its  host. 

The  eggs  are  scattered  with  the  feces  of  the  host  and  are  taken 
up  by  certain  beetle  larvae.  In  Europe  the  usual  intermediate  hosts 
are  the  larvae  of  the  cockchafer,  Melolontha  vulgaris,  or  of  the  flower 
beetle,  Cetonia  aurata.  Stiles  has  shown  that  in  the  United  States 
the  intermediate  host  is  the  larva  of  the  June  bug,  Lachnosterna 
(fig.  124).  It  is  probable  that  several  of  the  native  species  serve  in 
this  capacity. 

A  number  of  other  nematode  parasites  of  birds  and  mammals 
have  been  reported  as  developing  in  arthropods  but  here,  as  in  the 
case  of  the  cestodes,  experimental  proof  is  scant.  The  cases  above 
cited  are  the  better  established  and  will  ser^'e  as  illustrations. 


CHAPTER   VIII 

ARTHROPODS  AS  ESSENTIAL  HOSTS  OF  PATHOGENIC 
PROTOZOA 

Mosquitoes  and  Malaria 

Under  the  name  of  malaria  is  included  a  group  of  morbid  symp- 
toms formerly  supposed  to  be  due  to  a  miasm  or  bad  air,  but  now 
known  to  be  caused  by  protozoan  parasites  of  the  genus  Plasmodium, 
which  attack  the  red  blood  corpuscles.  It  occurs  in  paroxysms, 
each  marked  by  a  chill,  followed  by  high  fever  and  sweating.  The 
fever  is  either  intermittent  or  remittent. 

There  are  three  principal  types  of  the  disease,  due  to  different 
species  of  the  parasite.     They  are: 

1.  The  benign-tertian,  caused  by  Plasmodium  vivax,  which  under- 
goes its  schizogony  or  asexual  cycle  in  the  blood  in  forty-eight  hours, 
or  even  less.  This  type  of  the  disease, — characterized  by  fever 
every  two  days,  is  the  most  wide-spread  and  common. 

2.  The  quartan  fever  is  due  to  the  presence  of  Plasmodium 
malaricB,  which  has  an  asexual  cycle  of  seventy-two  hours,  and  there- 
fore the  fever  recurs  every  three  days.  This  type  is  more  prevalent 
in  temperate  and  sub-tropical  regions,  but  appears  to  be  rare  every- 
where. 

3.  The  sub-tertian  "sestivo-autumnal,"  or  "pernicious"  fever 
is  caused  by  Plasmodium  falciparum.  Schizogony  usually  occurs 
in  the  internal  organs,  particularly  in  the  spleen,  instead  of  in  the 
peripheral  circulation,  as  is  the  case  of  the  tertian  and  quartan  forms. 
The  fever  produced  is  of  an  irregular  type  and  the  period  of  schizogony 
has  not  been  definitely  determined.  It  is  claimed  by  some  that  the 
variations  are  due  to  different  species  of  malignant  parasites. 

It  is  one  of  the  most  wide-spread  of  human  diseases,  occurring 
in  almost  all  parts  of  the  world,  except  in  the  polar  regions  and  in 
waterless  deserts.     It  is  most  prevalent  in  marshy  regions. 

So  commonplace  is  malaria  that  it  causes  little  of  the  dread 
inspired  by  most  of  the  epidemic  diseases,  and  yet,  as  Ross  says, 
it  is  perhaps  the  most  important  of  human  diseases.  Figures  regard- 
ing its  ravages  are  astoimding.  Celli  estimated  that  in  Italy  it 
caused  an  average  annual  mortality  of  fifteen  thousand,  representing 
about  two  million  cases.     In  India  alone,  according  to  Ross  (19 10) 

186 


Mosquitoes  and  Malaria  187 

"it  has  been  offieially  estimated  to  cause  a  mean  annual  death-rate 
of  five  per  thousand;  that  is,  to  kill  every  year,  on  the  average,  one 
million  one  hundred  and  thirty  thousand."  In  the  United  States 
it  is  widespread  and  though  being  restricted  as  the  country  develops, 
it  still  causes  enormous  losses.  During  the  year  191 1,  "in  Alabama 
alone  there  were  seventy  thousand  cases  and  seven  hundred  and 
seventy  deaths."  The  weakening  effects  of  the  disease,  the  invasion 
of  other  diseases  due  to  the  attacks  of  malaria,  are  among  the  very 
serious  results,  but  they  cannot  be  estimated. 

Not  only  is  there  direct  effect  on  man,  but  the  disease  has  been  one 
of  the  greatest  factors  in  retarding  the  development  of  certain  regions. 
Everywhere  pioneers  have  had  to  face  it,  and  the  most  fertile  regions 
have,  in  many  instances  been  those  most  fully  dominated  by  it. 
Herrick  (1903)  has  presented  an  interesting  study  of  its  effects  on 
the  development  of  the  southern  United  States  and  has  shown  that 
some  parts,  which  are  among  the  most  fertile  in  the  world,  are 
rendered  practically  uninhabitable  by  the  ravages  of  malaria.  How- 
ard (1909)  estimates  that  the  annual  money  loss  from  the  disease 
in  the  United  States  is  not  less  than  $100,000,000. 

It  was  formerly  supposed  that  the  disease  was  due  to  a  miasm, 
to  a  noxious  effluvia,  or  infectious  matter  rising  in  the  air  from 
swamps.  In  other  words  its  cause  was,  as  the  name  indicated 
"mal  aria,"  and  the  deep  seated  fear  of  night  air  is  based  largely  on 
the  belief  that  this  miasm  was  given  off  at  night.  Its  production 
was  thought  to  be  favored  by  stirring  of  the  soil,  dredging  operations 
and  the  like. 

The  idea  of  some  intimate  connection  between  malaria  and 
mosquitoes  is  not  a  new  one.  According  to  Manson,  Lancisi  noted 
that  in  some  parts  of  Italy  the  peasants  for  centimes  have  believed 
that  malaria  is  produced  by  the  bite  of  mosquitoes.  Celli  states 
that  one  not  rarely  hears  from  such  peasants  the  statement  that 
"In  such  a  place,  there  is  much  fever,  because  it  is  full  of  mosquitoes." 
Koch  points  out  that  in  German  East  Africa  the  natives  call  malaria 
and  the  mosquito  by  the  same  name,  Mbu.  The  opinion  was  not 
lacking  support  from  medical  men.  Celli  quotes  passages  from  the 
writings  of  the  Italian  physician,  Lancisi,  which  indicate  that  he 
favored  the  \dew  in  1 7 1 7 . 

Dr.  Josiah  Nott  is  almost  universally  credited  with  having  sup- 
ported the  theory,  in  1848,  but  as  we  have  already  pointed  out 
his  work  has  been  misinterpreted.  The  statements  of  Beauperthuy, 
(1853)  were  more  explicit. 


1 88  Arthropods  as  Hosts  of  Pathogenic  Protozoa 

The  clearest  early  presentation  of  the  circumstantial  evidence  in 
favor  of  the  theory  of  mosquito  transmission  was  that  of  A.  F.  A. 
King,  an  American  physician,  in  1883.  He  presented  a  series  of 
epidemiological  data  and  showed  "how  they  may  be  explicable  b}' 
the  supposition  that  the  mosquito  is  the  real  source  of  the  disease, 
rather  than  the  inhalation  or  cutaneous  absorption  of  a  marsh  vapor." 
We  may  well  give  the  space  to  summarizing  his  argument  here  for 
it  has  been  so  remarkably  substantiated  by  subsequent  work: 

1.  Malaria,  like  mosquitoes,  affects  by  preference  low  and  moist 
localities,  such  as  swamps,  fens,  jungles,  marshes,  etc. 

2.  Malaria  is  hardly  ever  developed  at  a  lower  temperature 
than  60°  Fahr.,  and  such  a  temperature  is  necessary  for  the  develop- 
ment of  the  mosquito. 

3.  Mosquitoes,  like  malaria,  may  both  accumulate  in  and  be 
obstructed  by  forests  lying  in  the  course  of  winds  blowing  from 
malarious  localities. 

4.  By  atmospheric  currents  malaria  and  mosquitoes  are  alike 
capable  of  being  transported  for  considerable  distances. 

5.  Malaria  may  be  developed  in  previously  healthy  places  by 
turning  up  the  soil,  as  in  making  excavations  for  the  foundation  of 
houses,  tracks  for  railroads,  and  beds  for  canals,  because  these  opera- 
tions afford  breeding  places  for  mosquitoes. 

6.  In  proportion  as  countries,  previously  malarious,  are  cleared 
up  and  thickly  settled,  periodical  fevers  disappear,  because  swamps 
and  pools  are  drained  so  that  the  mosquito  cannot  readily  find  a  place 
suitable  to  deposit  her  eggs. 

7.  Malaria  is  most  dangerous  when  the  sun  is  down  and  the 
danger  of  exposure  after  sunset  is  greatly  increased  b>'  the  person 
exposed  sleeping  in  the  night  air.  Both  facts  are  readily  explicable 
by  the  mosquito  malaria  theory. 

8.  In  malarial  districts  the  use  of  fire,  both  indoors  and  to  those 
who  sleep  out,  affords  a  comparative  security  against  malaria,  because 
of  the  destruction  of  mosquitoes. 

9.  It  is  claimed  that  the  air  of  cities  in  some  wa}'  renders  the 
poison  innocuous,  for,  though  a  malarial  disease  may  be  raging  out- 
side, it  does  not  penetrate  far  into  the  interior.  We  may  easily 
conceive  that  mosquitoes,  while  invading  cities  during  their  nocturnal 
pilgrimages  will  be  so  far  arrested  by  walls  and  houses,  as  well  as 
attracted  by  lights  in  the  suburbs,  that  many  of  them  udll  in  this 
way  be  prevented  from  penetrating  "far  into  the  interior." 


Mosquitoes  and  Malaria  189 

10.  Malarial  diseases  and  like\vise  mosquitoes  are  most  prevalent 
toward  the  latter  part  of  summer  and  in  the  autumn. 

1 1 .  Various  writers  have  maintained  that  malaria  is  arrested  by 
canvas  curtains,  gauze  veils  and  mosquito  nets  and  have  recom- 
mended the  use  of  mosquito  curtains,  "through  which  malaria  can 
seldom  or  never  pass."  It  can  hardly  be  conceived  that  these 
intercept  marsh-air  but  they  certainly  do  protect  from  mos- 
quitoes. 

12.  Malaria  spares  no  age,  but  it  affects  infants  much  less 
frequently  than  adults,  because  young  infants  are  usually  carefully 
housed   and  protected  from  mosquito  inoculation. 

Correlated  with  the  miasmatic  theory  was  the  belief  that  some 
animal  or  ^^egetable  organism  which  lived  in  marshes,  produced 
malaria,  and  frequent  searches  were  made  for  it.  Salisbury  (1862) 
thought  this  causative  organism  to  be  an  alga,  of  the  genus  Palmella; 
others  attributed  it  to  certain  fungi  or  bacteria. 

In  1880,  the  French  physician,  Laveran,  working  in  Algeria, 
discovered  an  amoeboid  organism  in  the  blood  of  malarial  patients 
and  definitely  established  the  parasitic  nature  of  this  disease.  Pig- 
mented granules  had  been  noted  by  Meckel  as  long  ago  as  1847,  in 
the  spleen  and  blood  of  a  patient  who  had  died  of  malaria,  and  his 
observations  had  been  repeatedly  verified,  but  the  granules  had  been 
regarded  as  degeneration  products,  and  the  fact  that  they  occurred 
in  the  body  of  a  foreign  organism  had  been  overlooked. 

Soon  after  the  discovery  of  the  parasites  in  the  blood,  Gerhardt 
(1884)  succeeded  in  transferring  the  disease  to  healthy  individuals 
by  inoculation  of  malarious  blood,  and  thus  proved  that  it  is  a  true 
infection.  This  was  verified  by  numerous  experimenters  and  it 
was  found  that  inoculation  with  a  very  minute  quantity  of  the  dis- 
eased blood  would  not  only  produce  malaria  but  the  particular  type 
of  disease. 

Laveran  traced  out  the  life  cycle  of  the  malarial  parasite  as  it 
occurs  in  man.  The  details  as  we  now  know  them  and  as  they  are 
illustrated  by  the  accompanying  figure  125,  are  as  follows: 

The  infecting  organism  or  sporozoite,  is  introduced  into  the  cir- 
culation, penetrates  a  red  blood  corpuscle,  and  forms  the  amoeboid 
schizont.  This  lives  at  the  expense  of  the  corpuscle  and  as  it  develops 
there  are  deposited  in  its  body  scattered  black  or  reddish  black 
particles.  These  are  generally  called  melanin  granules,  but  are 
much  better  referred  to  as  haemozoin,  as  they  are  not  related  to 


igo 


Arthropods  as  Hosts  of  Pathogenic  Protozoa 


melanin.  The  hsemozoin  is  the  most  conspicuous  part  of  the  para- 
site, a  feature  of  advantage  in  diagnosing  from  unstained  prepara- 
tions. 

As  the  schizont  matures,  its  nucleus  breaks  up  into  a  nimiber  of 
daughter  nuclei,  each  with  a  rounded  mass  of  protoplasm  about  it, 
and  finally  the  corpuscles  are  broken  down  and  these  rounded  bodies 


125.     Life  cycle  of  the  malaria  parasite.     Adapted  from  Leuckart's  chart, 
by  Miss  Anna  Stryke. 

are  liberated  in  the  plasma  as  merozoites.  These  merozoites  infect 
new  cor|Duscles  and  thus  the  asexual  cycle  is  continued.  The  malarial 
paroxysm  is  coincident  with  sporulation. 

As  early  as  Laveran's  time  it  was  known  that  under  conditions 
not  yet  determined  there  are  to  be  found  in  the  blood  of  malarious 
patients  another  phase  of  the  parasite,  differing  in  form  according 
to  the  type  of  the  disease.  In  the  pernicious  type  these  appear  as 
large,  crescent-shaped  organisms  which  have  commonly  been  called 
"crescents."     We  now  know  that  these  are  sexual  forms. 


Mosquitoes  and  Malaria  191 

When  the  parasite  became  known  there  immediately  arose  specu- 
lations as  to  the  way  in  which  it  was  transferred  from  man  to  man. 
It  was  thought  by  some  that  in  nature  it  occurred  as  a  free-living 
amoeba,  and  that  it  gained  access  to  man  through  being  taken  up 
with  impure  water.  However,  niunerous  attempts  to  infect  healthy 
persons  by  having  them  drink  or  inhale  marsh  water,  or  by  injecting 
it  into  their  circulation  resulted  in  failure,  and  influenced  by  Leuckart's 
and  Melnikoff 's  work  on  DipyUdium,  that  of  Fedtschenko  on  Dracun- 
culus,  and  more  especially  by  that  of  Manson  on  Filaria,  search  was 
made  for  some  insect  which  might  transfer  the  parasite. 

Laveran  had  early  suggested  that  the  role  of  carrier  might  be 
played  by  the  mosquito,  but  Manson  first  clearly  formulated  the 
hyopthesis,  and  it  was  largely  due  to  his  suggestions  that  Ross  in 
India,  undertook  to  solve  the  problem.  With  no  knowledge  of  the 
form  or  of  the  appearance  in  this  stage,  or  of  the  species  of  mosquito 
concerned,  Ross  spent  almost  two  and  a  half  years  of  the  most  arduous 
work  in  the  search  and  finally  in  August,  1897,  seventeen  years 
after  the  discovery  of  the  parasite  in  man,  he  obtained  his  first 
definite  clue.  In  dissecting  a  "dappled-winged  mosquito,"  "every 
cell  was  searched  and  to  my  intense  disappointment  nothing  what- 
ever was  foimd,  until  I  came  to  the  insect's  stomach.  Here,  however, 
just  as  I  was  about  to  abandon  the  examination,  I  saw  a  very  delicate 
circular  cell,  apparently  l^^ing  amongst  the  ordinary  cells  of  the  organ 
and  scarcely  distinguishable  from  them.  On  looking  further, 
another  and  another  similar  object  presented  itself.  I  now  focused 
the  lens  carefiilly  on  one  of  these,  and  found  that  it  contained  a  few 
minute  granules  of  some  black  substance,  exactly  like  the  pigment  of 
the  parasite  of  malaria.  I  coiuited  altogether  twelve  of  these  cells 
in  the  insect." 

Further  search  showed  that  "the  contents  of  the  mature  pigment 
cells  did  not  consist  of  clear  fluid  but  of  a  multitude  of  delicate, 
thread-like  bodies  which  on  the  rupture  of  the  parent  cell,  were  poured 
into  the  body  cavity  of  the  insect.     They  were  evidently  spores." 

With  these  facts  established,  confirmation  and  extension  of 
Ross's  results  quickly  followed,  from  many  different  sources.  We 
■cannot  trace  this  work  in  detail  but  will  only  point  out  that  much 
of  the  credit  is  due  to  the  Italian  workers,  Grassi,  Bignami,  and 
Bastianelli,  and  to  Koch  and  Daniels. 

It  had  already  been  found  that  when  fresh  blood  was  mounted  and 
properly  protected  against  evaporation,  a  peculiar  change  occurred 


1 92  Arthropods  as  Hosts  of  Pathogenic  Protozoa 

in  these  crescents  after  about  half  an  hour's  time.  From  certain 
of  them  there  were  pushed  out  long  whip-like  processes  which  moved 
with  a  very  active,  lashing  movement.  The  parasite  at  this  stage 
is  known  as  the  "flagellated  body."  Others,  differing  somewhat  in 
details  of  structure,  become  rounded  but  do  not  give  off  "fiagella." 

The  American  worker,  MacCallimi  (1897),  in  studying  bird 
malaria  as  found  in  crows,  first  recognized  the  true  nature  of  these 
bodies.  He  regarded  them  as  sexual  forms  and  believed  that  the 
so-called  fiagella  played  the  part  of  spermatozoa.  Thus,  the  "flagel- 
lated body"  is  in  reality  a  micro  gametohlast,  producing  micro  gametes, 
or  the  male  sexual  element,  while  the  others  constitute  the  macro- 
gametes,  or  female  elements. 

It  was  found  that  when  blood  containing  these  sexual  forms  was 
sucked  up  by  an  Anopheline  mosqmto  and  taken  into  its  stomach,  a 
microgamete  penetrated  and  fertilized  a  macrogamete  in  a  way 
analogous  to  what  takes  place  in  the  fertilization  of  the  egg  in  higher 
forms.  The  resultant,  mobile  organism  is  known  as  the  migratory 
ookinete.  In  this  stage  the  parasite  bores  through  the  epithelial 
lining  of  the  "stomach"  (mid-intestine)  of  the  mosquito  and  becomes 
encysted  under  the  muscle  layers.  Here  the  oocyst,  as  it  is  now 
known,  matures  and  breaks  up  into  the  bod}^  cavity  and  finally 
its  products  come  to  lie  in  the  salivary  glands  of  the  mosquito.  Ten 
to  twelve  days  are  required  for  these  changes,  after  which  the  mos- 
quito is  infective,  capable  of  introducing  the  parasite  with  its  saliva, 
when  feeding  upon  a  healthy  person. 

Thus  the  malarial  parasite  is  known  to  have  a  double  cycle,  an 
alternation  of  generations,  of  which  the  asexual  stage  is  undergone  in 
man,  the  sexual  in  certain  species  of  mosquitoes.  The  mosquito  is 
therefore  the  definitive  host  rather  than  the  intermediate,  as  usually 
stated. 

The  complicated  cycle  may  be  made  clearer  by  the  diagram  of 
Miss  Str>^ke  (191 2)  which,  by  means  of  a  double-headed  mosquito 
(fig.  126)  endeavors  to  show  how  infection  takes  place  through  the 
biting  of  the  human  victim,  (at  A),  in  whom  asexual  miiltiplication 
then  takes  place,  and  how  the  sexual  stages,  taken  up  at  B  in  the 
diagram,  are  passed  in  the  body  of  the  mosquito. 

The  experimental  proof  that  mosquitoes  of  the  Anopheline  group 
are  necessary  agents  in  the  transmission  of  malaria  was  afforded  in 
1900  when  two  English  physicians,  Drs.  Sambon  and  Low  lived  for 
the  three  most  malarial  months  in  the  midst  of  the  Roman  Campagna, 


Mosquitoes  and  Malaria 


193 


a  region  famous  for  centuries  as  a  hot-bed  of  malaria.     The  two 
experimenters  moved   about  freely  throughout  the  day,   exposed 


126.     Life  cycle  of  the  malarial  parasite.     After  Miss  Anna  Stryke. 

themselves  to  rains  and  all  kinds  of  weather,  drank  marsh  water, 
slept  exposed  to  the  marsh  air,  and,  in  short,  did  everything  which 
was  supposed  to  cause  malaria,  except  that  they  protected  them- 
selves thoroughly  from  mosquito  bites,  retiring  at  sunset  to  a  mosquito- 


194 


Arthropods  as  Hosts  of  Pathogenic  Protozoa 


proof  hut.  Though  they  took  no  quinine  and  all  of  their  neighbors 
suffered  from  malaria,  they  were  absolutely  free  from  the  disease. 
To  complete  the  proof,  mosquitoes  which  had  fed  in  Rome  on 
malarious  patients  were  sent  to  England  and  allowed  to  bite  two 
volunteers,  one  of  them  Dr.  Manson's  own  son,  who  had  not  been 
otherwise  exposed  to  the  disease.  Both  of  these  gentlemen  con- 
tracted typical  cases  of  malaria  and  the  parasites  were  to  be  found  in 
abundance  in  their  blood. 

Since  that  timic  there  have  been  many  practical  demonstrations 
of  the  fact  that  malaria  is  transmitted  exclusively  by  the  bite  of 

mosquitoes  and  that  the  destruc- 
tion of  the  mosquitoes  means  the 
elimination  of  the  disease. 

We  have  said  that  the  malarial 
parasite  is  able  to  undergo  its 
development  only  in  certain 
species  of  mosquitoes  belonging 
to  the  Anopheline  group.  It  is 
by  no  means  certain  that  all  of 
this  group  even,  are  capable  of 
acting  as  the  definitive  host  of 
the  parasites,  and  much  careful 
experiment  work  is  still  needed 
along  this  line.  In  the  United 
States,  several  species  have  been 
found  to  be  implicated,  Anopheles 
quadrimaculatus  and  Anopheles 
The  characteristics  of  these  species 
and  the  distinctions  between  them  and  other  mosquitoes  mil  be 
discussed  in  Chapter  XII. 

In  antimalarial  work  it  is  desirable  to  distinguish  the  anopheline 
mosquitoes  from  the  culicine  species  in  all  stages.  The  following 
tabulation  presents  the  more  striking  distinctions  between  the  groups 
as  represented  in  the  United  States. 


127.     Eggs  of  Anopheles.    After  Howard. 


crucians  being  the  most  common. 


Anopheles 
Eggs:  Laid  singly  in  small 
numbers  upon  the  surface  of  the 
water.  Eggs  lie  upon  their  sides 
and  float  by  means  of  lateral 
expansions  (fig.  127). 


Culex,  Aedes,  etc. 
Deposited  in  clumps  in  the 
form  of  a  raft  (Culex  group)  or 
deposited  singly  in  the  water  or 
on  the  ground  in  places  which 
may  later  be  submerged. 


Mosquitoes  and  Malaria 


195 


Larva:  When  at  rest  floats  in 
a  horizontal  position  beneath  the 
surface  film.  No  respiratory 
tube  but  instead  a  flattened 
area  on  the  eighth  abdominal 
segment  into  which  the  two 
spiracles  open  (fig.  128). 

Adults:  Palpi  in  both  sexes 
nearly  or  quite  as  long  as  the 
proboscis.  Proboscis  projecting 
forward  nearly  on  line  with  the 
axis  of  the  body.  When  at  rest 
on  a  vertical  wall  the  body  is 
usually  held  at  an  angle  with  the 
vertical  (fig.  128).  Wings  fre- 
quently spotted  (fig.  130). 


When  at  rest  (with  few  excep- 
tions) floats  suspended  in  an 
oblique  or  vertical  position,  or 
more  rarely  nearly  horizontal, 
with  the  respiratory  tube  in 
contact  with  the  surface  film 
(fig.  128). 

Palpi  short  in  the  female,  in 
the  male  usually  elongate.  Pro- 
boscis projects  forward  at  an 
angle  with  the  axis  of  the  body. 
When  at  rest  on  a  vertical  wall 
the  body  is  usually  held  parallel 
or  the  tip  of  the  abdomen  in- 
clined towards  the  wall  (fig.  128). 
Wings  usually  not  spotted. 


(o)  Normal  position  of  the  lar- 
vae of  Culex  and  Anopheles  in 
the  water.  Culex,  left;  Ano- 
pheles, middle;  Culex  pupa, 
right  hand  figure. 


These    malarial-bearing    species    are    essentially    domesticated 
mosquitoes.     They  develop  in  any  accumulation  of  water  which 

stands  for  a  week  or  more. 
Ponds,  puddles,  rain  barrels, 
horse  troughs,  cess-pools,  cans, 
even  the  foot-prints  of  ani- 
mals in  marshy  ground  may 
afford  them  breeding  places. 
It  is  clear  from  what  has  been  said  regarding  the  life  cycle  of  the 
malarial  parasite  that  the  mosquito  is  harmless  if  not  itself  diseased. 
Hence  malarial-bearing  species  may  abound  in  the 
neighborhood  where  there  is  no  malaria,  the  disease 
being  absent  simply  because  the  mosquitoes  are  unin- 
fected. Such  a  locality  is  potentially  malarious  and 
needs  only  the  introduction  of  a  malarial  patient  who  is 
exposed  to  the  mosquitoes.  It  is  found  that  such  patients 
may  harbor  the  parasites  in  their  blood  long  after  they 
ar6  apparently  well  and  thus  may  serve  as  a  menace, 
just  as  do  the  so-called  typhoid  carriers.  In  some 
malarious  regions  as  high  as  80-90  per  cent  of  the  natives 
are  such  malaria-carriers  and  must  be  reckoned  with  in 
antimalaria  measures.  128.  (6)  Norma 

Based  upon  our  present  day  knowledge  of  the  life  cycle      c°ui'e  x^'i  nd 
of  the  malarial   parasite   the  fight  against  the  disease      fhT^afi!^  °" 


196 


Arthropods  as  Hosts  of  Pathogenic  Protozoa 


becomes  primarily  a  problem  in  economic  entomolog\% — it  is  a  ques- 
tion of  insect  control,  in  its  broadest  interpretation. 

The  lines  of  defence  and  offence 

against  the  disease  as   outlined  by 

Boyce  (1909)  are' 

1.  Measures  to  avoid  the  reser- 
voir (man) : 

Segregation. 
Screening  of  patients. 

2 .  Measures  to  avoid  Anopheles : 
Choice   of    suitable    locality, 

when  possible. 
Screening      of     houses     and 

porches. 
Sleeping  under  mosquito  nets. 

3.  Measures  to  exterminate  the 
Anopheles : 

Use  of  natural  enemies. 

Use  of  culicides,  oiling  ponds, 

etc. 
Drainage  and   scavenging  to 

destroy  breeding  places. 
Enforcement  of  penalties  for 

harboring  larvse  or  keeping 

stagnant  water. 
Educational  methods. 
4.     Systematic  treatment  with  quinine  to  exterminate  theparasites. 

Mosquitoes  and  Yellow  Fever 

Yellow  fever  was  until  recently  one  of  the  most  dreaded  of  epi- 
demic diseases.  It  is  an  acute,  specific  and  infectious  disease,  non- 
contagious in  character  but  occurring  in  epidemics,  or  endemics, 
within  a  peculiarly  limited  geographical  area.  It  is  highly  fatal, 
but  those  who  recover  are  generally  immune  from  subsequent  at- 
tacks. 

It  is  generally  regarded  as  an  American  disease,  having  been 
found  by  Cortez,  in  Mexico,  and  being  confined  principal^  to  the 
American  continents  and  islands.  It  also  occurs  in  Africa  and  at- 
tempts have  been  made  to  show  that  it  was  originally  an  African 
disease  but  there  is  not  sufficient  evidence  to  establish  this  view. 


129.     Larva  of  Anopheles.     After  Howard. 


Mosquitoes  and  Yellow  Fever 


197 


There  have  been  man}-  noted  outbreaks  in  the  United  States. 
Boston  suffered  from  it  in  1691  and  again  in  1693;  New  York  in 
1668  and  as  late  as  1856;  Baltimore  in  1819.  In  1793  occurred  the 
great  epidemic  in  Philadelphia,  with  a  death  rate  of  one  in  ten  of  the 
population.  In  the  past  century  it  was  present  almost  every  year  in 
some  locality  of  our  Southern  States,  New  Orleans  being  the  greatest 
sufferer.  In  the  latter  city  there  were  7848  deaths  from  the  disease 
in  1853,  4854  in  1858,  and  4046  in  1878.     The  last  notable  outbreak 


130.     Anopheles  quadrimaculatus.  male  and  female.  (xsM)-     After  Howard. 

was  in  1905.  Reed  and  Carroll  (1901)  estimated  that  during  the 
period  from  1793  to  1900  there  had  not  been  less  than  500,000  cases 
in  the  United  States. 

As  in  the  case  of  the  plague,  the  most  stringent  methods  of  con- 
trol proved  ineffective  and  helplessness,  almost  hopelessness  marked 
the  great  epidemics.  A  vivid  picture  of  conditions  is  that  given  by 
Mathew  Car}-,  1793  (quoted  by  Kelly,  1906)  in  "A  Short  Account  of 
the  Malignant  Fever  Lately  Prevalent  in  Philadelphia." 

"The  consternation  of  the  people  of  Philadelphia  at  this  period 
was  carried  beyond  all  bounds.     Dismay  and  affright  were  visible 


ipS 


Arthropods  as  Hosts  of  Pathogenic  Protozoa 


in  the  countenance  of  almost  every  person.  Of  those  who  remained, 
many  shut  themselves  in  their  houses  and  were  afraid  to  walk  the 
streets.  *  *  *  The  corpses  of  the  most  respectable  citizens, 
even  those  who  did  not  die  of  the  epidemic,  were  carried  to  the  grave 
on  the  shafts  of  a  chair  (chaise),  the  horse  driven  by  a  negro,  un- 
attended by  friends  or  relative,  and  without  any  sort  of  ceremony. 


131.     Anopheles  punctipennis.     Female,  (X4).     After  Howard. 

People  hastily  shifted  their  course  at  the  sight  of  a  hearse  coming 
toward  them.  Many  never  walked  on  the  footpath,  but  went  into 
the  middle  of  the  streets  to  avoid  being  infected  by  passing  by  houses 
wherein  people  had  died.  Acquaintances  and  friends  avoided  each 
other  in  the  streets  and  only  signified  their  regard  by  a  cold  nod. 
The  old  custom  of  shaking  hands  fell  into  such  disuse  that  many 
shrunk  back  with  affright  at  even  the  offer  of  the  hand.     A  person 


Mosquitoes  and  Yellow  Fever 


199 


with  a  crape,  or  any  ai^pearance  of  mourning  was  shunned  1  ke  a 
viper.  And  many  valued  themselves  highly  on  the  skill  and  address 
with  which  they  got  to  the  windward  of  every  person  they  met. 
Indeed,  it  is  not  v^robable  that  London,  at  the  last  stage  of  the  plague, 
exhibited  stronger  marks  of  terror  than  were  to  be  seen  in  Phila- 


132.     Anopheles  crucians.     Female  (x4).     After  Howard. 


delphia  from  the  24th  or  25th  of  August  until  pretty  late  in  Septem- 
ber." 

Such  was  the  condition  in  Philadelphia  in  1793  and,  as  far  as 
methods  of  control  of  the  disease  were  concerned,  there  was  practi- 
cally no  advance  during  the  last  century.  The  dominant  theory 
was  that  yellow  fever  was  spread  by  fomites,  that  is,  exposed  bedding, 
clothing,  baggage,  and  the  like.  As  late  as  1898  a  bulletin  of  the 
United  States  Marine  Hospital  Service  stated: 


200 


Arthropods  as  Hosts  of  Pathogenic  Protozoa 


"While  yellow  fever  is  a  communicable  disease,  it  is  not  con- 
tagious in  the  ordinary  acceptance  of  the  term,  but  is  spread  by  the 
infection  of  places  and  articles  of  bedding,  clothing,  and  furniture." 

Based  upon  this  theory,  houses,  baggage,  freight,  even  mail, 
were  disinfected,  and  the  most  rigid  quarantine  regulations  were 
enforced.  The  hardships  to  which  people  of  the  stricken  regions 
were  subjected  and  the  financial  losses  are  incalculable.  And  withal, 
the  only  efhcient  check  upon  the  disease  seemed  to  be  the  heavy  frosts. 


133.     Culex  sollicitans.     Female  (X4).     After  Howard. 


It  was  found  that  for  some  reason,  the  epidemic  abated  with  cold 
weather, — a  measure  beyond  human  control. 

It  is  not  strange  that  among  the  multitude  of  theories  advanced  to 
explain  the  cause  and  method  of  dissemination  of  the  disease  there 
should  be  suggestions  that  yellow  fever  was  transmitted  by  the 
mosquito.  We  have  seen  that  Beauperthuy  (1855)  clearly  urged 
this  theory. 

More  detailed,  and  of  the  greatest  influence  in  the  final  solution 
of  the  problem  were  the  arguments  of  Dr.  Carlos  Finlay,  of  Havana. 
In  1 88 1,  in  a  paper  presented  before  the  "Rea  Academia  de  Ciencias 
Medicas,  Fisicis  y  Naturales  de  la  Habana,"  he  said: 


Mosquitoes  and  Yellow  Fever  201 

"I  feel  convinced  that  any  theory  which  attributes  the  origin  and 
the  propagation  of  yellow  fever  to  atmospheric  influences,  to  mias- 
matic or  meteorological  conditions,  to  filth,  or  to  the  neglect  of  general 
hygienic  precautions,  must  be  considered  as  utterly  indefensible." 

He  postulated  the  existence  of  a  material  transportable  substance 
causing  yellow  fever, — ^"something  tangible  which  requires  to  be 
conveyed  from  the  sick  to  the  health}^  before  the  disease  can  be 
propagated"  and  after  discussing  the  peculiarities  of  the  spread  of 
the  disease  and  the  influence  of  meteorological  conditions,  he  decides 
that  the  carriers  of  the  disease  must  be  sought  among  insects.  He 
continues : 

"On  the  other  hand,  the  fact  of  yellow  fever  being  characterized 
both  clinically  and  (according  to  recent  findings)  histologically,  by 
lesions  of  the  blood  vessels  and  by  alterations  of  the  physical  and 
chemical  conditions  of  the  blood,  suggested  that  the  insect  which 
should  convey  the  infectious  particles  from  the  patient  to  the  healthy 
should  be  looked  for  among  those  which  drive  their  sting  into  blood 
vessels  in  order  to  suck  human  blood.  Finally,  b}'  reason  of  other 
considerations  which  need  not  be  stated  here,  I  came  to  think  that 
the  mosquito  might  be  the  transmitter  of  yellow  fever." 

"Assimilating  the  disease  to  small-pox  and  to  vaccination,  it 
occurred  to  me  that  in  order  to  inoculate  yellow  fever  it  would  be 
necessarv^  to  pick  out  the  inoculable  material  from  within  the  blood 
\'essels  of  a  yellow  fever  patient  and  to  carry  it  like^vise  into  the 
interior  of  a  blood  vessel  of  a  person  who  was  to  be  inociilated.  All 
of  which  conditions  the  mosquito  satisfies  most  admirably  through 
its  bite." 

In  the  course  of  his  study  of  the  problem,  Finlay  made  detailed 
studies  of  the  life  history  and  habits  of  the  common  mosquitoes  at 
Ha^'ana,  and  arrived  at  the  conclusion  that  the  carrier  of  the  yellow 
fever  was  the  Culex  mosquito  or  Aedes  calopus,  as  it  is  now  known. 
With  this  species  he  undertook  direct  experimental  tests,  and  be- 
lieved that  he  succeeded  in  transmitting  the  disease  by  the  bite  of 
infected  mosquitoes  in  three  cases.  Unfortunately,  possibility 
of  other  exposure  was  not  absolutely  excluded,  and  the  experiments 
attracted  little  attention. 

Throughout  the  next  twenty  years  Finlay  continued  his  work  on 
yellow  fever,  modifying  his  original  theory  somewhat  as  time  went  on. 
Among  his  later  suggestions  was  that  in  the  light  of  Smith's  work 
on  Texas  fever,  his  theorv  must  be  "somewhat  modified  so  as  to 


202  Arthropods  as  Hosts  of  Pathogenic  Protozoa 

include  the  important  circumstance  that  the  faculty  of  transmitting 
the  yellow  fever  germ  need  not  be  limited  to  the  parent  insect, 
dir,ectly  contaminated  by  stinging  a  yellow  fever  patient  (or  per- 
haps by  contact  with  or  feeding  from  his  discharges),  but  may  be 
likewise  inherited  by  the  next  generation  of  mosquitoes  issued  from 
the  contaminated  parent."  He  believed  that  the  bite  of  a  single 
mosquito  produced  a  light  attack  of  the  disease  and  was  thus  effec- 
tive in  immunizing  the  patient.  Throughout  the  period,  many 
apparently  successful  attempts  to  transmit  the  disease  by  mosqui- 
toes were  made.  In  the  light  of  present  day  knowledge  we  must 
regard  these  as  defective  not  only  because  possibility  of  other  infec- 
tion was  not  absolutely  excluded  but  because  no  account  was  taken 
of  the  incubation  period  within  the  body  of  the  mosquito. 

In  1900,  while  the  American  army  was  stationed  in  Cuba  there 
occurred  an  epidemic  of  yellow  fever  and  an  army  medical  board  was 
appointed  for  "the  puq^ose  of  pursuing  scientific  investigations  with 
reference  to  the  acute  infectious  diseases  prevalent  on  the  island." 
This  was  headed  by  Walter  Reed  and  associated  with  him  were  James 
Carroll,  Jesse  W.  Lazear  and  Aristides  Agramonte,  the  latter  a  Cuban 
immune.  For  a  detailed  summary  of  this  work  the  lay  reader  can- 
not do  better  than  read  Dr.  Kelly's  fascinating  biography  "Walter 
Reed  and  Yellow  Fever." 

Arriving  at  the  army  barracks  near  Havana  the  Commission  first 
took  up  the  study  of  Bacillus  icter aides,  the  organism  which  Sanarelli, 
an  Italian  physician,  had  declared  the  causative  agent  in  yellow  fever. 
They  were  unable  to  isolate  this  bacillus  either  from  the  blood  during 
life  or  from  the  blood  and  organs  of  cadavers  and  therefore  turned 
their  attention  to  Finlay's  theory  of  the  propagation  of  yellow  fever 
by  means  of  the  mosquito.  In  this  work  they  had  the  unselfish 
and  enthusiastic  support  of  Dr.  Finlay  himself,  who  not  only  consulted 
with  them  and  placed  his  publications  at  their  disposal,  but  furnished 
eggs  from  which  their  experimental  mosquitoes  were  obtained. 
Inoculations  of  eleven  non-immunes  through  the  bite  of  infected 
mosquitoes  were  made,  and  of  these,  two  gave  positive  results.  The 
first  of  the  two  was  Dr.  Carroll  who  allowed  himself  to  be  bitten 
by  a  mosquito  which  had  been  caused  to  feed  upon  four  cases  of 
yellow  fever,  two  of  them  severe  and  two  mild.  The  first  patient 
had  been  bitten  twelve  days  before. 

Three  days  after  being  bitten.  Dr.  Carroll  came  down  with  a 
typical  case  of  yellow  fever.     So  se\'ere  was  the  attack  that  for  three 


Mosquitoes  and  Yellow  Fever  203 

days  his  lite  hung  in  the  balance.  During  his  convalescence  an 
incident  occurred  which  showed  how  the  theor}^  of  mosquito  trans- 
mission of  the  disease  was  generally  regarded.  We  quote  from  Dr. 
Kelly:  "One  of  his  nurses  who  came  from  Tennessee  had  had  con- 
siderable experience  with  yellow  fever,  having  indeed,  lost  her  hus- 
band and  several  children  from  it.  One  day  early  in  his  illness  Dr. 
Carroll  mentioned  to  her  that  he  had  contracted  the  disease  through 
the  bite  of  a  mosquito,  and  noticed  that  she  looked  surprised.  Some 
time  later,  when  well  enough  to  look  over  the  daily  records  of  his 
condition,  he  found  this  entry:  'vSa^^s  he  got  his  illness  through  the 
bite  of  a  mosquito, — delirious'." 

The  second  case  was  that  of  an  American  who  was  bitten  by  four 
mosquitoes,  two  of  which  had  bitten  severe  (fatal)  cases  of  yellow 
fever  twelve  days  pre\aously,  one  of  which  had  bitten  a  severe  case 
(second  day)  sixteen  days  before  and  one  which  had  bitten  a  severe 
case  eight  days  before.  Five  days  later,  the  subject  developed  a  well 
pronounced  but  mild  case  of  the  disease. 

In  the  meantime,  another  member  of  the  Commission,  Dr.  Lazear, 
was  accidentally  bitten  by  a  mosquito  while  collecting  blood  from 
yellow  fever  patients.  Five  days  later  he  contracted  a  typical  case 
which  resulted  fatally. 

So  clear  was  the  evidence  from  these  preliminary  experiments 
that  the  commission  felt  warranted  in  announcing,  October  27,  1900, 
that,  "The  mosquito  serves  as  the  intermediate  host  for  the  parasite 
of  yellow  fever,  and  it  is  highly  probable  that  the  disease  is  only 
propagated  through  the  bite  of  this  insect." 

In  order  to  extend  the  experimental  evidence  under  conditions 
which  could  leave  no  possibility  of  infection  from  other  sources,  a 
special  experimental  sanitary  station,  named  in  honor  of  the  deceased 
member  of  the  Commission,  was  estabhshed  in  an  open  field  near 
the  town  of  Quemados,  Cuba.  Here  there  were  constructed  two  small 
buildings  known  respectively  as  the  "infected  clothing  building" 
and  the  "infected  mosquito  building." 

The  infected  clothing  building,  14  x  20  feet  in  size,  was  purposely 
so  constructed  as  to  exclude  anything  like  efficient  ventilation,  but 
was  thoroughly  screened  to  prevent  the  entrance  of  mosquitoes. 
Into  this  building  were  brought  sheets,  pillow-slips,  blankets,  etc., 
contaminated  by  contact  with  cases  of  yellow  fever  and  their  dis- 
charges,— ^many  of  them  purposely  soiled  with  a  liberal  quantity  of 
black  vomit,  urine,  and  fecal  matter  from  patients  sick  with  yellow 


204  Arthropods  as  Hosts  of  Pathogenic  Protozoa 

fever.  Nothing  could  better  serve  as  the  fomites  which  were  sup- 
posed to  convey  the  dread  disease. 

Three  non-immunes  unpacked  these  articles,  giving  each  a 
thorough  handling  and  shaking  in  order  to  disseminate  through  the 
air  of  the  room  the  specific  agent  of  the  disease.  They  were  then 
used  in  making  up  the  beds  which  the  volunteers  occupied  each  night 
for  a  period  of  twenty  days.  The  experiment  was  repeated  three 
times,  volunteers  even  sleeping  in  the  soiled  garments  of  yellow  fever 
victims  but  in  not  a  single  case  was  there  the  slightest  symptom  of 
disease.  The  theory  of  the  spread  of  yellow  fever  by  fomites  was 
completely  demolished. 

The  infected  mosquito  building,  equal  in  size  to  its  companion, 
was  the  antithesis  as  far  as  other  features  were  concerned.  It  was 
so  constructed  as  to  give  the  best  possible  ventilation,  and  bedding 
which  was  brought  into  it  was  thoroughly  sterilized.  Like  the 
infected  clothing  building  it  was  carefully  screened,  but  in  this  case 
it  was  in  order  to  keep  mosquitoes  in  it  as  well  as  to  prevent  entrance 
of  others.  Through  the  middle  of  the  room  ran  a  mosquito-proof 
screen. 

On  December  5,  1900,  a  non-immune  volunteer  who  had  been  in 
the  quarantine  camp  for  fifteen  days  and  had  had  no  other  possible 
exposure,  allowed  himself  to  be  bitten  by  five  mosquitoes  which  had 
fed  on  yellow  fever  patients  fifteen  or  more  days  previously.  The 
results  were  fully  confirmatory  of  the  earlier  experiments  of  the 
Commission — at  the  end  of  three  days,  nine  and  a  half  hours,  the 
subject  came  down  with  a  well  marked  case  of  yellow  fever. 

In  all,  ten  cases  of  experimental  yellow  fever,  caused  by  the  bite 
of  infected  mosquitoes  were  developed  in  Camp  Lazear.  Through- 
out the  period  of  the  disease,  other  non-immunes  slept  in  the  little 
building,  separated  from  the  patient  only  b}'  the  mosquito-proof 
screen,  but  in  no  circumstances  did  they  suffer  any  ill  effects. 

It  was  found  that  a  yellow  fever  patient  was  capable  of  infecting 
mosquitoes  only  during  the  first  three  or  four  days  after  coming 
down  with  the  disease.  Moreover,  after  the  mosquito  has  bitten 
such  a  patient,  a  period  of  at  least  twelve  days  must  elapse  before 
the  insect  is  capable  of  transmitting  the  disease. 

Once  the  organism  has  undergone  its  twelve  day  development, 
the  mosquito  may  remain  infective  for  weeks.  In  experiments  of 
the  Commission,  two  of  the  mosquitoes  transmitted  the  disease  to  a 
volunteer   fiftv-seven    days    after   their    contamination.     No    other 


Mosquitoes  and  Yellow  Fever  205 

volunteers  presenting  themselves,  one  of  these  mosquitoes  died  the 
sixty-ninth  and  one  the  seventy-first  day  after  their  original  con- 
tamination, without  it  being  determined  whether  they  were  still 
capable  of  transmitting  the  disease. 

So  carefully  carried  out  was  this  work  and  so  conclusi\'e  were  the 
results  that  Dr.  Reed  was  justified  in  writing: 

"Six  months  ago,  when  we  landed  on  this  island,  absolutely  noth- 
ing was  known  concerning  the  propagation  and  spread  of  yellow 
fever — it  was  all  an  unfathomable  mystery — but  today  the  curtain 
has  been  drawn— its  mode  of  propagation  is  established  and  we  know 
that  a  case  minus  mosquitoes  is  no  more  dangerous  than  one  of 
chills  and  fever." 

The  conclusions  of  the  Commission  were  fully  substantiated  by 
numerous  workers,  notably  Dr.  Guiteras  of  the  Havana  Board  of 
Health,  who  had  taken  a  lively  interest  in  the  work  and  whose 
results  were  made  known  in  1901,  and  by  the  Brazilian  and  French 
Commission  at  Sao  Paulo,  Brazil,  in  1903. 

Throughout  the  work  of  the  Army  Commission  and  down  to  the 
present  time  many  fruitless  efforts  have  been  made  to  discover  the 
specific  organism  of  yellow  fever.  It  was  clearly  established  that 
the  claims  of  Sanarelli  for  Bacillus  icteroides  were  wdthout  founda- 
tion. It  was  found,  too,  that  whatever  the  infective  agent  might 
be  it  was  capable  of  passing  through  a  Berkefeld  filter  and  thus  be- 
longs to  the  puzzling  group  of  "filterable  viruses."  It  was  further 
found  that  the  virus  was  destroyed  by  heating  up  to  55°  C  for  ten 
minutes.     It  is  generally  beheved  that  the  organism  is  a -Protozoan. 

The  question  of  the  hereditary  transmission  of  the  yellow  fever 
organism  within  the  mosquito  was  left  unsettled  by  the  Army  Com- 
mission, though,  as  we  have  seen,  it  was  raised  by  Finlay.  Marchoux 
and  Simond,  of  the  French  Commission  devoted  much  attention  to 
this  phase  of  the  problem  and  basing  their  conclusions  on  one  ap- 
parently positive  case,  they  decided  that  the  disease  could  be  trans- 
mitted through  the  egg  of  an  infected  A'edes  calopus  to  the  second 
generation  and  thence  to  man.  The  conclusion,  which  is  of  very 
great  importance  in  the  control  of  yellow  fever,  has  not  been  \-erified 
by  other  workers. 

Once  clearly  established  that  3'ellow  fever  was  transmitted  solely 
by  mosquitoes,  the  question  of  the  characteristics,  habits,  and  geo- 
graphical distribution  of  the  insect  carrier  became  of  vital  import- 
ance. 


2o6 


Arthropods  as  Hosts  of  Pathogenic  Protozoa 


Aedes  calopus,  more  conunonly  known  as  Stegomyia  fasciata  or 
Siegomyia  calopus  (fig.  134)  is  a  moderate  sized,  rather  strikingly 
marked  mosquito.  The  general  color  is  dark-brown  or  reddish- 
brown,  but  the  thorax  has  a  conspicuous  broad,  silvery -white  curved 
line  on  each  side,  with  two  parallel  median  silvery  lines.     Between 

the  latter  there  is  a 
slender,  broken  line. 
The  whole  gives  a  lyre- 
shaped  pattern  to  the 
thorax.  The  abdomen 
is  dark  with  silvery- 
white  basal  bands  and 
silvery  white  spots  on 
each  side  of  the  ab- 
dominal segments. 
Legs  black  with  rings 
of  pure  white  at  the 
base  of  the  segments. 
Size  of  the  female 
3.3  to  5  mm.;  male  3 
to  4.5  mm. 

It  is  pre-eminently 
a  domesticated  species , 
being  found  almost 
exclusively  about  the 
habitation  of  man. 
"Its  long  association 
with  man  is  shown  by 
many  of  its  habits.  It 
approaches  stealthily 
from  behind.  It  re- 
treats upon  the  slight- 
est alarm.  The  ankles  and,  when  one  is  sitting  at  a  table  or  desk, 
the  underside  of  the  hands  and  wrists  are  favorable  points  of  attack. 
It  attacks  silently,  whereas  other  mosquitoes  have  a  piping  or  hum- 
ming note.  The  warning  sound  has  doubtless  been  suppressed  in 
the  evolutionary  process  of  its  adaptation  to  man.  It  is  extremely 
wary.  It  hides  whenever  it  can,  concealing  itself  in  garments, 
working  into  the  pockets,  and  under  the  lapels  of  coats,  and  crawl- 
ing up  under  the  clothes  to  bite  the  legs.       In  houses,  it  will  hide 


134. 


The  yellow  fever  mosquito  (Aedes  calopus),  (x?). 
After  Howard. 


Mosquitoes  and  Yellow  Fever 


207 


in  dark  comers,  under  picture  moldings  and  behind  the  heads  of 
old-fashioned  bedsteads.  It  will  enter  closets  and  hide  in  the  folds 
of  garments." — Howard. 

It  was  claimed  by  the  French  Commission,  and  subsequently 
often  stated  in  discussions  of  the  relation  of  the  mosquito  to  yellow 
fever  that  the  mature  Aedes  calopus  will  bite  only  at  night.  If  this 
were  true  it  would  be  of  the  greatest  importance  in  measures  to 
avoid  the  disease.  Unfortunately,  the  claim  was  illy  founded  and 
numerous  workers  have  clearly  established  that  the  exact  converse 
is  more  nearly  true,  this  mosquito  being  pre-eminently  a  day  species, 
feeding  most  actively  in  early  morning, 
about  sunrise,  and  late  in  the  afternoon. 
On  cloudy  days  it  attacks  at  any  time 
during  the  day.  Thus  there  is  peril  in 
the  doctrine  that  infected  regions  may 
be  visited  with  perfect  safety  during 
the  daytime  and  that  measures  to 
avoid  the  mosquito  attack  need  be 
taken  only  at  night. 

Dr.  Finlay  maintained  that  the 
adult,  even  when  starved,  would  not 
bite  when  the  temperature  was  below 
23°  C,  but  subsequent  studies  have 
shown  that  this  statement  needs  modi- 
fication. The  French  Commission, 
working  at  Rio  de  Janeiro,  found  that  Aedes  calopus  would  bite 
regularly  at  temperatures  between  22°  and  25°  and  that  the  optimum 
temperature  was  between  27°  and  30°  C,  but  their  experiments  led 
them  to  believe  that  it  would  bite  in  nature  at  a  temperature  as 
low  as  17°  C. 

'  '  The  yellow  fever  mosquito  breeds  in  cisterns,  water  barrels, 
pitchers  and  in  the  various  water  receptacles  about  the  house.  In 
our  own  Southern  States  it  very  commonly  breeds  in  the  above- 
ground  cisterns  which  are  in  general  use.  Often  the  larvae  (fig.  1356) 
are  found  in  flower  vases,  or  even  in  the  little  cups  of  water  which 
are  placed  under  the  legs  of  tables  to  prevent  their  being  overrun  by 
ants.  They  have  been  repeatedly  found  breeding  in  the  holy  water 
font  in  churches.  In  short,  they  breed  in  any  collection  of  water  in 
close  proximity  to  the  dwellings  or  gathering  places  of  man. 


13.5a.     Aedes  calopus. 
After  Howaid. 


Pupa. 


208 


Arthropods  as  Hosts  of  Pathogenic  Protozoa 


The  life  cycle  under  favorable  conditions  is  completed  in  from 
twelve  to  fifteen  days.  These  figures  are  of  course  very  dependent 
upon  the  temperature.  The  Army  Commission  in  Cuba  found  that 
the  cycle  might  be  completed  in  as  brief  a  i^eriod  as  nine  and  a  half 
days.     Under  less  favorable  conditions  it  may  be  greatly  lengthened. 

The  adults  are  long  lived.  We  have 
seen  that  during  the  experimental  work 
in  Cuba  specimens  were  kept  in  cap- 
tivity for  sixty-nine  and  seventy-one 
days,  respectively,  and  that  they  were 
proved  to  retain  their  infectivity  for  at 
least  fifty-seven  days.  Dr.  Guiteras 
subsequently  kept  an  infected  adult  for 
one  hundred  and  fifty-four  days. 

Low  temperatures  have  a  very  great 
effect  not  only  on  development,  but  on 
the  activity  and  even  life  of  the  adults. 
Long  before  the  method  of  transmission 
of  yellow  fever  was  discovered  it  was  well 
known  that  the  epidemics  were  brought 
to  a  close  by  heavy  frosts,  and  it  is  now 
known  that  this  is  due  to  the  killing  of 
the  mosquitoes  which  alone  could  spread 
the  disease. 

Aedes  calopus  has  a  very  wide  distri- 
bution since,  as  Howard  says,  being  a 
domestic  mosquito,  having  a  fairly  long 
life  in  the  adult  stage,  and  having  the 
custom  of  hiding  itself  in  the  most  ingen- 
ious ways,  it  is  particularly  subject  to  car- 
riage for  long  distances  on  board  vessels, 
in  railway  trains,  even  packed  in  baggage.  In  general,  its  permanent 
distribution  is  from  40  degrees  north  latitude  to  40  degrees  south 
latitude  (Brumpt),  in  a  belt  extending  around  the  world.  In  the 
United  States  it  breeds  in  most  of  our  Southern  States. 

Thus,  as  in  the  case  of  malaria,  there  are  many  places  where  the 
insect  carrier  is  abundant  but  where  yellow  fever  does  not  occur. 
Such,  for  instance,  are  Hawaii,  Australia  and  Asia.  An  outbreak  may 
occur  at  any  time  that  a  patient  suffering  from  the  disease  is  allowed 
to  enter  and  become  a  source  of  infection  for  the  mosquitoes.     In 


1356.    Aedes  calopus;    larva.  (x7). 
After  Howard. 


Mosquitoes  and  Yellow  Fever  209 

this  connection  various  writers  have  called  attention  to  the  menace 
from  the  Panama  Canal.  When  it  is  completed,  it  will  allow  of 
direct  passage  from  regions  where  yellow  fever  is  endemic  and  this 
will  greatly  increase  the  possibility  of  its  introduction  into  these  places 
where  it  is  now  unknown.  The  result,  with  a  wholly  non-immune 
population,  would  be  appalling. 

On  the  other  hand,  there  are  places  wholly  outside  of  the  normal 
range  of  Aedes  calopus  where  the  disease  has  raged.  Such  are  New 
York,  Boston,  and  even  Philadelphia,  which  have  suffered  notable 
epidemics.  These  outbreaks  have  been  due  to  the  introduction  of 
infected  mosquitoes  during  the  heat  of  summer,  when  they  have  not 
only  conveyed  the  disease  but  have  found  conditions  favorable 
for  their  multiplication.  Or,  uninfected  mosquitoes  have  been  thus 
accidentally  brought  in  and  developed  in  large  numbers,  needing 
then  only  the  accidental  introduction  of  cases  of  the  disease  to  start 
an  epidemic. 

Methods  of  control  of  various  diseases  have  been  revolutionized 
by  the  discovery  that  they  were  insect -borne,  but  in  no  other  case 
has  the  change  been  as  radical  or  the  results  as  spectacular  as  in  the 
case  of  yellow  fever.  The  "shot-gun  quarantine,"  the  sufferings  and 
horrors,  the  hopelessness  of  fighting  absolutely  blindly  have  given 
way  to  an  efficient,  clear-cut  method  of  control,  based  upon  the  knowl- 
edge that  the  disease  is  carried  from  man  to  man  solely  by  the  mosqui- 
to, A'edes  calopus.  The  lines  of  defense  and  offense  are  essentially 
as  follows : 

In  the  first  place,  when  a  case  of  yellow  fever  occurs,  stringent 
precautions  must  be  adopted  to  prevent  the  infection  of  mosquitoes 
and  the  escape  of  any  already  infected.  This  means  that  the  patient 
must  be  removed  to  a  mosquito-proof  room,  or  ward  beyond  reach  of 
the  insects,  and  that  the  infected  room  must  be  thoroughly  fumi- 
gated at  once,  to  kill  the  mosquitoes  hiding  within  it.  All  cracks 
and  openings  should  be  closed  with  strips  of  paper  and  fumigation 
with  burning  sulphur  or  pyrethrum  carefully  carried  out. 

It  should  be  remembered  that  if  the  first  case  noted  is  that  of  a 
resident  rather  than  imported,  it  means  that  the  mosquito  carriers 
became  infected  more  than  two  weeks  before  the  case  was  diagnosed, 
for  as  we  have  seen,  the  germ  must  undergo  a  twelve-day  period  of 
development  within  its  insect  host.  Therefore  a  careful  search  must 
be  made  for  mild  cases  which,  though  unrecognized,  may  serv^e  as 
foci  for  the  spread  of  the  disease. 


210  Arthropods  as  Hosts  of  Pathogenic  Protozoa 

In  face  of  a  threatened  epidemic  one  of  the  most  essential  measures 
is  to  educate  the  citizens  and  to  gain  their  complete  cooperation  in 
the  fight  along  modem  lines.  This  may  be  done  through  the  schools, 
the  pulpit,  places  of  amusement,  newspapers  and  even  bulletin 
boards. 

Emphasis  should  be  placed  on  the  necessity  of  both  non-immunes 
and  immunes  using  mosquito  curtains,  and  in  all  possible  ways 
avoiding  exposure  to  the  mosquitoes. 

Then  the  backbone  of  the  fight  must  be  the  anti-mosquito  meas- 
ures. In  general,  these  involve  screening  and  fumigating  against 
adults,  and  control  of  water  supply,  oiling,  and  drainage  against  the 
larvae.  The  region  involved  must  be  districted  and  a  thorough  survey 
undertaken  to  locate  breeding  places,  which  must,  if  possible, 
be  eradicated.  If  they  are  necessary  for  water  supplies,  such  as 
casks,  or  cisterns,  they  should  be  carefully  screened  to  prevent 
access  of  egg-laying  adults. 

The  practical  results  of  anti-mosquito  measures  in  the  fight 
against  yellow  fever  are  well  illustrated  by  the  classic  examples  of 
the  work  in  Havana,  immediately  following  the  discoveries  of  the 
Army  Commission  and  by  the  stamping  out  of  the  New  Orleans 
epidemic  in  1905. 

The  opportunities  for  an  immediate  practical  application  of  the 
theories  of  the  Army  Commission  in  Havana  were  ideal.  The  city 
had  always  been  a  hotbed  of  yellow  fever  and  was  the  principal 
source  from  which  the  disease  was  introduced  year  after  year  into 
our  Southern  States.  It  was  under  martial  law  and  with  a  military 
governor  who  was  himself  a  physician  and  thoroughly  in  sympathy 
with  the  views  of  the  Commission,  the  rigid  enforcement  of  the 
necessary  regulations  was  possible.  The  story  of  the  first  campaign 
has  been  often  told,  but  nowhere  more  clearly  than  in  Dr.  Reed's 
own  account,  published  in  the  Journal  of  Hygiene  for  1902. 

Closer  home  was  the  demonstration  of  the  efficacy  of  these 
measures  in  controlling  the  yellow  fever  outbreak  in  New  Orleans 
in  1905.  During  the  spring  and  early  summer  of  the  year  the  disease 
had,  unperceived,  gained  a  firm  foothold  in  that  city  and  when,  in 
early  July  the  local  Board  of  Health  took  cognizance  of  its  existence, 
it  was  estimated  that  there  had  been  in  the  neighborhood  of  one 
hundred  cases. 

Conditions  were  not  as  favorable  as  they  had  been  under  martial 
law  in  Havana  for  carrying  on  a  rigid  fight  along  anti-mosquito  lines. 


Mosquitoes  and  Yellow  Fever  211 

The  densel}'  populated  city  was  unprepared,  the  pubhc  had  to  be 
educated,  and  an  efficient  organization  built  up.  The  local  authori- 
ties actively  began  a  general  fight  against  the  mosquito  but  in  spite 
of  their  best  efforts  the  disease  continued  to  spread.  It  was  recog- 
nized that  more  rigid  organization  was  needed  and  on  August  12th 
the  United  States  Public  Health  and  Marine  Hospital  Service  was 
put  in  absolute  charge  of  the  fight.  Up  to  this  time  there  had  been 
one  hundred  and  forty-two  deaths  from  a  total  of  nine  hundred  and 
thirteen  cases  and  all  of  the  conditions  seemed  to  threaten  an  out- 
break to  exceed  the  memorable  one  of  1878  when,  as  we  have  seen 
there  were  four  thousand  and  forty-six  deaths. 

With  the  hearty  cooperation  of  the  citizens, — ^physicians  and 
laymen  alike, — the  fight  was  waged  and  long  before  frost  or  any  near 
approach  thereto  the  disease  was  stamped  out, — a  thing  unheard  of 
in  previous  epidemics.  The  total  loss  of  life  was  four  hundred  and 
sixty — about  11  per  cent  as  great  as  that  from  the  comparable  epi- 
demic of  1878.  If  the  disease  had  been  promptly  recognized  and 
combated  ^^^th  the  energ}^  which  marked  the  fight  later  in  the  sum- 
mer, the  outbreak  wotdd  have  made  little  headway  and  the  great 
proportion  of  these  lives  would  have  been  saved. 


CHAPTER  IX 
ARTHROPODS    AS    ESSENTIAL    HOSTS    OF  PATHOGENIC  PROTOZOA 


Insects  and  Trypanosomiases 

By  trypanosomiasis  is  meant  a  condition  of  animal  parasitism, 
common  to  man  and  the  lower  animals,  in  which  trypanosomes, 
peculiar  flagellate  protozoa,  infest  the  blood.  Depending  upon  the 
species,  they  may  be  harmless,  producing  no  appreciable  ill-effect, 
or  pathogenic,  giving  rise  to  conditions  of  disease.  A  number  of 
these  are  known  to  be  transferred  by  insects. 

In  order  that  we  may 
consider  more  fully  the 
developmental  stage  of 
these  parasites  within 
their  insect  host,  it  is 
necessary  that  we  des- 
cribe briefly  the  structure 
of  the  blood-inhabiting 
stage. 

The  trypanosomes  are 
elongated,  usually  point- 
ed, flagellated  protozoa 
(fig.  136)  in  which  the 
single  flagellum,  bent 
under  the  body,  forms  the 
outer  limit  of  a  delicate  undulating  membrane.  It  arises  near 
one  end  of  the  organism  from  a  minute  centrosome-like  body 
which  is  known  as  the  blepheroplast,  and  at  the  opposite  end  extends 
for  a  greater  or  less  distance  as  a  free  flagellum.  Enclosing,  or 
close  beside  the  blepheroplast  is  the  small  kinetonucleus.  The 
principal  nucleus,  round  or  oval  in  form,  is  situated  near  the  center 
of  the  body.  Asexual  reproductions  occiu-s  in  this  stage,  by  longi- 
tudinal fission,  the  nucleus  and  the  blepheroplast  dividing  independ- 
ently of  one  another.  From  the  blepheroplast  of  one  of  the  daughter 
cells  a  new  flagellum  is  formed. 

Among  the  pathogenic  species  are  to  be  found  the  causative 
organisms  of  some  of  the  most  serious  diseases  of  domestic  animals 
and  even  of  man.     It  is  probable  that  these  pathogenic  species  secrete 


136.     Trypanosomc  brucei.     After  Bruce. 


Fleas  and  Lice  as  Carriers  of  Trypanosoma  lewisi  213 

a  specific  poison.      The  majority    of  them  are  tropical  in  distri- 
bution. 

Though  we  are  concerned  especially  with  the  species  which  infest 
man,  we  shall  first  consider  two  of  the  trypanosomes  of  lower  animals, 
known  long  before  an}'  of  those  of  man  had  been  found. 

Fleas  and  Lice  as  Carriers  of  Trypanosoma  lewisi. — Trypanosoma 
lewisi,  the  first  mammalian  trypanosomc  known,  is  to  be  found  in  the 
blood  of  wild  rats.  Like  its  host,  it  appears  to  be  cosmopolitan  in 
distribution,  having  been  reported  from  several  localities  in  the 
United  States,  Brazil,  Argentine,  England,  Germany,  France,  Italy, 
Russia,  Asia  and  Africa. 

This  species  is  usually  regarded  as  non-pathogenic,  but  in  experi- 
mental work,  especially  with  white  rats,  heavy  infestations  often 
result  fatally,  and  naturally  infested  specimens  sometimes  show 
evidence  of  injury.  Rats  which  have  been  infested  exhibit  at  least 
temporary  immunity  against  new  infection. 

Trypanosoma  lewisi  is  transmitted  from  rat  to  rat  by  fleas  and 
by  lice.  Rabinowitsch  and  Kempner  (1899)  first  found  that  healthy 
rats  which  were  kept  with  infested  rats,  showed  trypanosomes  in 
their  blood  after  about  two  weeks.  They  found  the  trypanosomes 
in  the  alimentary  canal  of  fleas  which  had  fed  on  the  diseased  rats. 
On  teasing  such  fleas  in  physiological  salt  solution  and  inoculating 
them  into  fresh  rats  they  were  able  to  produce  the  infection.  Finally, 
they  showed  that  the  fleas  which  had  fed  upon  infested  rats  were 
able  to  carry  the  parasites  to  healthy  rats.  Corresponding  experi- 
ments with  lice  were  not  successful.  Prowazek  UQ^S)  found  in  the 
rat  louse  {Hcematopinus  spinulosus)  organisms  which  he  regarded 
as  developmental  stages  of  the  Trypanosoma  lewisi.  He  believed 
that  the  sexual  cycle  was  undergone  in  this  insect. 

Nuttall  (1908)  readily  transmitted  the  trypanosomes  through  the 
agency  of  fleas,  (Ceratophyllus  fasciatus  and  Ctenopthalmus  agyrtes). 
He  believes  that  these  insects  are  probably  the  chief  transmitters 
of  the  parasite.  He  was  also  able  to  transmit  it  from  diseased  to 
healthy  rats  through  the  agency  of  the  rat  louse.  He  was  unable 
to  trace  any  developmental  stages  in  the  louse  and  inclined  to  the 
opinion  that  Prowazek  was  deceived  by  the  presence  of  extraneous 
flagellates  such  as  are  known  to  exist  in  a  number  of  blood-sucking 
arthropods. 

Nuttall  concludes  that  since  three  distinct  kinds  of  blood-sucking 
insects  are  capable  of  transmitting  Trypanosoma  lewisi  it  appears 


214        Arthropods  as  Essential  Hosts  of  Pathogenic  Protozoa 

doubtful  that  this  flagellate  is  a  parasite  of  the  invertebrate  "host" 
in  the  sense  claimed  by  Prowazek  and  other  investigators. 

Tsetse-flies  and  Nagana — One  of  the  greatest  factors  in  retarding 
the  de^^elopment  of  certain  regions  of  Africa  has  been  the  presence 
of  a  small  fly,  little  larger  than  the  common  house-fly.  This  is  the 
tsetse-fly,  Glossina  morsitans  (fig.  165)  renoAvned  on  account  of  the 
supposed  virulence  of  its  bite  for  cattle,  horses  and  other  domestic 
mammals. 

The  technical  characteristics  of  the  tsetse-flies,  or  Glossinas,  and 
their  several  species,  will  be  found  in  a  later  chapter.  We  need 
emphasize  only  that  they  arc  blood-sucking  Muscidse  and  that, 
unlike  the  mosquitoes,  the  sexes  resemble  each  other  closely  in  struc- 
ture of  the  mouth-parts,  and  in  feeding  habits. 

In  1894,  Colonel  David  Bruce  discovered  that  the  fly  was  not  in 
itself  poisonous  but  that  the  deadly  effect  of  its  bite  was  due  to  the 
fact  that  it  transmitted  a  highly  pathogenic  blood  parasite,  Trypano- 
soma brucei.  This  trypanosome  Bruce  had  discovered  in  the  blood 
of  South  African  cattle  suffering  from  a  highly  fatal  disease  known  as 
"nagana".  On  inoculating  the  blood  of  infected  cattle  into  horses 
and  dogs  he  produced  the  disease  and  found  the  blood  teeming  with 
the  causative  organism.  In  the  course  of  his  work  he  established 
beyond  question  that  the  "nagana"  and  the  tsetse-fly  disease  were 
identical. 

Tsetse-flies  of  the  species  Glossina  morsitans,  which  fed  upon 
diseased  animals,  were  found  capable  of  giving  rise  to  the  disease 
in  healthy  animals  up  to  forty-eight  hours  after  feeding.  Wild 
tsetse-flies  taken  from  an  infected  region  to  a  region  where  they  did 
not  normally  occur  were  able  to  transmit  the  disease  to  healthy 
animals.  It  was  found  that  many  of  the  wild  animals  in  the  tsetse- 
fly  regions  harbored  Trypanosoma  brucei  in  their  blood,  though  they 
showed  no  evidence  of  disease.  As  in  the  case  of  natives  of  malarial 
districts,  these  animals  acted  as  reservoirs  of  the  parasite.  Non- 
immune animals  subjected  to  the  attacks  of  the  insect  carrier,  quickly 
succumbed  to  the  disease. 

A  question  of  prime  importance  is  as  to  whether  the  insect  serves 
as  an  essential  host  of  the  pathogenic  protozoan  or  whether  it  is  a 
mere  mechanical  carrier.  Bruce  inclined  to  the  latter  view.  He  was 
unable  to  find  living  tr3'panosomes  in  the  intestines  or  excrements 
of  the  fly  or  to  produce  the  disease  on  the  many  occasions  when  he 


Tsetse-flies  and  Nagana  215 

injected  the  excrement  into  healthy  animals.  Moreover,  he  had 
found  that  the  experimental  flies  were  infective  only  during  the  first 
forty-eight  hours  and  that  if  wild  flies  were  taken  from  the  infected 
region,  "kept  without  food  for  three  days  and  then  fed  on  a  healthy 
dog,  they  never  gaVe  rise  to  the  disease." 

Koch  Had  early  described  what  he  regarded  as  sexual  forms  from 
the  intestine  of  the  fly  but  it  remained  for  Kleine  (1909)  to  experi- 
mentally demonstrate  that  a  part  of  the  life  cycle  of  the  parasite 
was  undergone  in  the  fly.  Working  with  Glossina  palpalis,  he  foimd 
that  for  a  period  of  ten  days  or  longer  after  feeding  on  an  animal 
sufteiing  from  nagana  it  was  non -infective,  but  that  then  it  became 
infective  and  was  able  to  transmit  the  disease  for  weeks  thereafter. 
He  discovered  and  described  developmental  stages  of  the  parasite 
wathin  the  intestine  of  the  insect.  In  other  words,  the  tsetse-fly 
(in  nature,  Glossina  morsitans),  serves  as  an  essential  host,  within 
which  an  important  part  of  the  life  cycle  of  the  parasite  is  undergone. 
These  conclusions  were  quickly  verified  by  Bruce  and  numerous 
other  workers  and  are  no  longer  open  to  question.  Klein  and  Taute 
are  even  inclined  to  think  that  mechanical  transmission  plays  practi- 
cally no  role  in  nature,  unless  the  fly  is  interrupted  while  feeding 
and  passes  immediately  to  a  new  animal. 

Tsetse-flies  and  Sleeping  Sickness  of  Man — About  the  beginning 
of  the  present  century  a  hitherto  little  known  disease  of  man  began 
to  attract  great  attention  on  accoimt  of  its  ravages  in  Uganda  and 
the  region  of  Victoria  N3^anza  in  South  Africa.  It  was  slow,  insidu- 
ous  and  absolutely  fatal,  characterized  in  its  later  stages  by  dullness, 
apathy,  and  finally  absolute  lethargy  all  day  long,  symptoms  which 
gave  it  the  name  of  "sleeping  sickness." 

It  was  soon  found  that  the  disease  was  not  a  new  one  but  that  it 
had  been  known  for  over  a  hundred  years  on  the  west  coast  of  Africa. 
Its  introduction  into  Central  and  East  Africa  and  its  rapid  spread 
have  been  attributed  primarily  to  the  development  of  the  country, 
the  formation  of  new  trade  routes  and  the  free  mingling  of  native 
tribes  formerly  isolated.  It  is  estimated  that  in  the  first  ten  years 
of  the  present  century  there  were  approximately  two  hundred 
thousand  deaths  from  the  disease  in  the  Uganda  protectorate.  In 
the  British  province  Bugosa,  on  the  Victoria  Nyanza  there  were 
thirty  thousand  deaths  in  the  period  from  1902-1905. 


2i6        Arthropods  as  Essential  Hosts  of  Pathogenic  Protozoa 

While  the  disease  is  pecuharly  African  there  are  a  number  of 
instances  of  its  accidental  introduction  into  temperate  regions. 
Slaves  suffering  from  it  were  occasionally  brought  to  America  in 
the  early  part  of  the  last  century  and  cases  have  sometimes  been 
imported  into  England.  In  none  of  the  cases  did  the  disease  gain  a 
foothold  or  spread  at  all  to  other  individuals. 

In  1902  Button  described  a  trypanosome,  T.  gambiense,  which  he 
and  Forde  had  found  the  year  before  in  the  blood  of  a  patient  suffer- 
ing from  a  pcculair  type  of  fever  in  Gambia.  In  1 902-1 903  Castel- 
lani  found  the  same  parasite  in  the  cerebro-spinal  fluid  of  sleeping- 
sickness  patients  and  definitely  reported  it  as  the  causative  organism 
of  the  disease.  His  work  soon  found  abundant  confirmation,  and 
it  was  discovered  that  the  sleeping  sickness  was  but  the  ultimate 
phase  of  the  fever  discovered  by  Button  and  Forde. 

When  Castellani  made  known  his  discoverv^  of  the  trypanosome 
of  sleeping  sickness,  Brumpt,  in  France,  and  vSambon,  in  England, 
independently  advanced  the  theory  that  the  disease  was  transmitted 
by  the  tsetse-fly,  Glossina  palpalis.  This  theory  was  based  upon  the 
geographical  distribution  and  epidemiology^  of  the  disease.  Since 
then  it  has  been  abimdantly  verified  by  experimental  evidence. 

Fortunately  for  the  elucidation  of  problems  relating  to  the  methods 
of  transfer  of  sleeping  sickness,  Trypanosoma  gambiense  is  patho- 
genic for  many  species  of  animals.  In  monkeys  it  produces  symptoms 
very  similar  to  those  caused  in  man.  Bruce  early  showed  that 
Glossina  palpalis  "fed  on  healthy  monkeys  eight,  twelve,  twenty-four 
and  forty-eight  hours  after  having  fed  on  a  native  suffering  from 
tr\'panosomiasis,  invariably  transmitted  the  disease.  After  three 
days  the  flies  failed  to  transmit  it."  In  his  summary  in  Osier's 
Modem  Medicine,  he  continues  "But  this  is  not  the  only  proof  that 
these  flies  can  carry  the  infective  agent.  On  the  lake  shore  there 
was  a  large  native  population  among  whom  we  had  found  about 
one-third  to  be  harboring  trypanosomes  in  their  blood.  The  tsetse- 
flies  caught  on  this  lake  shore,  brought  to  the  laboratory  in  cages, 
and  placed  straightway  on  healthy  monkeys,  gave  them  the  disease 
in  every  instance,  and  furnished  a  startling  proof  of  the  danger  of 
loitering  along  the  lake  shore  among  those  infected  flies." 

As  in  the  case  of  nagana,  Bruce  and  most  of  the  earlier  investi- 
gators supposed  the  transmission  of  the  sleeping  sickness  trypano- 
some by  Glossina  palpalis  to  be  purely  mechanical.  The  work  of 
Kleine  (1909)  clearly  showed  that  for  Trypanosoma  gambiense  as 


Tsetse-flies  and  Sleeping  Sickness  of  Man  217 

well  as  for  Trypanosoma  brucei  the  fly  served  as  an  essential  host. 
Indeed,  Kleine  and  many  subsequent  investigators  are  inclined  to 
think  that  there  is  practically  no  mechanical  transmission  of  trypan- 
osomes  from  animal  to  animal  by  Glossina  in  nature,  and  that  the 
many  successful  experiments  of  the  earlier  in^'estigators  were  due 
to  the  fact  that  they  used  A\'ild  flies  whi' h  already  harbored  the 
transfonned  parasite  rather  than  directly  inoculated  it  from  the 
blood  of  the  diseased  experimental  animals.  While  the  criticism 
is  applicable  to  some  of  the  work,  this  extreme  \T.ew  is  not  fully 
justified  by  the  evidence  at  hand. 

Kleine  states  (191 2)  that  Glossina  palpalis  can  no  longer  be 
regarded  as  the  sole  transmitter  of  sleeping  sickness.  Taute  (191 1) 
had  shown  that  under  experimental  conditions  Glossina  niorsitans 
was  capable  of  transferring  the  disease  and  Kleine  calls  attention  to 
the  fact  that  in  German  East  Africa,  in  the  district  of  the  Rovuma 
Ri^^er,  at  least  a  dozen  cases  of  the  disease  have  occurred  recently, 
though  only  Glossina  niorsitans  exists  in  the  district.  It  appears, 
however,  that  these  cases  are  due  to  a  different  parasite,  Trypano- 
soma rhodesiense.  This  species,  found  especially  in  north-east 
Rhodesia  and  in  Nyassaland,  is  transferred  by  Glossina  niorsitans. 

Other  workers  maintain  that  the  disease  ma}'  be  transmitted  by 
various  blood -sucking  flies,  or  even  bugs  and  lice  which  attack  man. 
Fullebom  and  Mayer  (1907)  have  shown  by  conclusive  experi- 
ments that  Aedes  (Stegomyia)  calopus  may  transmit  it  from  one 
animal  to  another  if  the  two  bites  immediately  succeed  each  other. 

It  is  not  possible  that  insects  other  than  the  tsetse-flies  (and  only 
certain  species  of  these),  play  an  important  role  in  the  transmission 
of  the  disease,  else  it  would  be  much  more  wide-spread.  Sambon 
(1908)  pointed  out  that  the  hypothesis  that  is  spread  by  Aedes 
calopus  is  opposed  by  the  fact  that  the  disease  never  spread  in  the 
Antilles,  though  frequently  imported  there  by  West  African  slaves. 
The  same  observation  would  apply  also  to  conditions  in  our  own 
Southern  States  in  the  early  part  of  the  past  century. 

Since  Glossina  palpalis  acts  as  an  essential  host  of  the  parasite 
and  the  chief,  if  not  the  only,  transmitter,  the  fight  against  sleeping 
sickness,  like  that  against  malaria  and  yellow  fever,  becomes  pri- 
marily a  problem  in  economic  entomology.  The  minutest  detail 
of  the  life-history,  biology,  and  habits  of  the  fly,  and  of  its  parasites 
and  other  natural  enemies  becomes  of  importance  in  attempts  to 
eradicate  the  disease.  Here  we  can  consider  only  the  general  features 
of  the  subject. 


2i8        Arthropods  as  Essential  Hosts  of  Pathogenic  Protozoa 

Glossina  palpalis  lives  in  limited  areas,  where  the  forest  and  under- 
growth is  dense,  along  the  lake  shore  or  river  banks.  According  to 
Hodges,  the  natural  range  from  shore  is  under  thirty  yards,  though 
the  distance  to  which  the  flies  may  follow  man  greatly  exceed  this. 

It  is  a  day  feeder,  a  fact  which  may  be  taken  advantage  of  in 
a^•oiding  exposure  to  its  attacks.  The  young  are  brought  forth  alive 
and  full-grown,  one  every  nine  or  ten  days.  Without  feeding,  they 
enter  the  ground  and  under  favorable  conditions,  complete  their 
development  in  a  month  or  more. 


>-tt" 


;'.:i.:  -lk:.!- ;s  concentration  camp  in  Ci 
("ominission. 


jf  German 


Methods  of  control  of  the  disease  must  look  to  the  prevention 
of  infection  of  the  flies,  and  to  their  avoidance  and  destruction. 
Along  the  first  line,  much  was  hoped  from  temporary  segregation 
of  the  sick  in  regions  where  the  fly  was  not  found.  On  the  assump- 
tion that  the  flies  acted  as  carriers  only  during  the  first  two  or  three 
days,  it  was  supposed  that  even  the  "fly  belts"  would  become  safe 
within  a  few  days  after  the  sick  were  removed.  The  problem  was 
found  to  be  a  much  more  diffictdt  one  when  it  was  learned  that  after 
a  given  brief  period  the  fly  again  became  infective  and  remained  so 
for  an  indeterminate  period.  Nevertheless,  isolation  of  the  sick 
is  one  of  the  most  important  measures  in  preventing  the  spread  of 


Sonth  American  Trypanosomiasis  219 

the  disease  into  new  districts.  Much,  too,  is  being  accompHshed 
by  moving  native  villages  from  the  fly  belts,     (c.f.  fig.  137.) 

All  measures  to  avoid  the  flies  should  be  adopted.  This  means 
locating  and  avoiding  the  fly  belts  as  far  as  possible,  careful  screen- 
ing of  houses,  and  protection  of  the  body  against  bites. 

Clearing  the  jungle  along  the  water  courses  for  some  yards  beyond 
the  natural  range  of  the  fly  has  proved  a  very  important  measure. 
Castellani  recommends  that  the  area  be  one  hundred  yards  and 
around  a  ^dllage  three  hundred  yards  at  least. 

Detailed  studies  of  the  parasites  and  the  natural  enemies  of  the 
tsetse-fly  are  being  undertaken  and  may  ultimately  yield  valuable 
results. 

South  American  Trypanosomiasis — The  tsetse-flies  are  distinc- 
tively African  in  distribution  and  until  recently  there  were  no  tryan- 
osomes  known  to  infest  man  in  America.  In  1909  Dr.  Chagas,  of 
Rio  de  Janeiro  described  a  new  species,  Trypanosoma  cruzi,  patho- 
genic to  man. 

Trypanosoma  cruzi  is  the  causative  organism  of  a  disease  common 
in  some  regions  of  Brazil,  where  it  is  known  as  "opilacao."  It  is 
especially  to  be  met  with  in  children  and  is  characterized  by  extreme 
anemia,  wasting,  and  stunted  development  associated  with  fever, 
and  enlargenemt  of  the  thyroid  glands.  The  disease  is  transmitted 
by  the  bites  of  several  species  of  assassin-bugs,  or  Reduviidae,  not- 
ably by  Conorhinus  megistus.  The  evolution  of  the  parasite  within 
the  bug  has  been  studied  especially  by  Chagas  and  by  Brumpt. 
From  the  latter's  text  we  take  the  following  summary. 

The  adult  tryanosomes,  ingested  by  a  Conorhinus  megistus,  of 
any  stage,  first  change  into  Crithidia-like  forms  and  then  those 
which  remain  in  the  stomach  become  ovoid  and  non-motile.  Brumpt 
found  these  forms  in  immense  numbers,  in  a  Cornohinus  which  had 
been  infested  fourteen  months  before.  The  forms  which  pass  into 
the  intestine  quickly  assume  the  Crithidia  form  and  continue  to 
develop  rapidly  under  this  form.  Some  weeks  later  they  e\^olve 
into  the  trypanosome  forms,  pathogenic  for  man.  The}^  then  pass 
out  with  the  excrement  of  the  bug  and  infect  the  vertebrate  host 
as  soon  as  they  come  in  contact  with  any  mucous  layer  (buccal, 
ocular  or  rectal).     More  rarely  they  enter  through  the  epidermis. 

Brumpt  showed  that  the  development  could  take  place  in  three 
species;   bed-bugs  (Cimex  lectidarius,  C.  hemipterus)  and  in  the  tick 


2  20         Arthropods  as  Essential  Hosts  of  Pathogenic  Protozoa 

Ornithodoros  mouhata.  The  e\^olution  proceeds  in  the  first  two 
species  of  bed-bugs  as  rapidly  as  in  Conorhinus,  or  even  more  rapidly, 
but  they  remain  infective  for  a  much  shorter  time  and  hence  Brumpt 
considers  that  they  play  a  much  less  important  role  in  the  spread  of 
the  disease. 

Conorhinus  megisttis,  like  related  forms  in  our  Southern  States, 
very  commonly  frequents  houses  and  attacks  man  with  avidity. 
Chagas  states  that  the  bites  are  painless  and  do  not  leave  any  traces. 
They  are  usually  inflicted  on  the  lips,  or  the  cheeks  and  thus  the 
buccal  mucosa  of  a  sleeper  may  be  soiled  by  the  dejections  of  the 
insect  and  the  bite  serving  as  a  port  of  entry  of  the  virus,  remain 
unnoticed. 

The  possibility  of  some  of  our  North  American  Reduviidae  play- 
ing a  similar  role  in  the  transmission  of  disease  should  not  be  over- 
looked. 

Leishmanioses  and  Insects — Closely  related  to  the  trypanosomes 
is  a  group  of  intracellular  parasites  which  have  recently  been  grouped 
by  Ross  under  the  genus  Leishmania.  Five  species  are  known  to 
affect  man.  Three  of  these  produce  local  skin  infestations,  but  two 
of  them,  Leishmania  donovani  and  L.  injantum,  produce  serious  and 
often  fatal  systemic  diseases. 

The  first  of  these,  that  produced  by  L.  donovani,  is  an  exceedingly 
virulent  disease  common  in  certain  regions  of  India  and  China.  It 
is  commonly  known  as  "Kala-azar,"  or  "dirm-dum"  fever,  and  more 
technically  as  tropical  leishmaniasis.  Patton  (1907)  believes  that 
the  parasite  is  transmitted  by  the  bed-bug  Cimex hemipterus,andh.as 
described  a  developmental  cycle  similar  to  that  which  can  be  found 
in  artificial  cultures.  On  the  other  hand,  Donovan  was  unable  to 
confirm  Patton's  work  and  believes  that  the  true  intermediate  host  is 
a  Reduviid  bug,  Conorhinus  ruhrojasciatus. 

Leishmania  injantum  is  the  cause  of  the  so-called  infantile  splenic 
leishmaniasis,  occurring  in  northern  Africa,  Spain,  Portugal,  Italy, 
and  possibly  other  parts  of  Europe.  The  parasite  occurs  habitually 
in  the  dog  and  is  only  accidentally  transferred  to  children,  Alvares 
and  da  Silva,  in  Portugal  (according  to  Brumpt,  19 13)  have  found 
that  the  excrement  of  a  flea  from  a  diseased  dog  contains  flagellates, 
and  they  suggest  that  the  infection  may  be  transmitted  by  the  acci- 
dental inoculation  of  this  excrement  by  means  of  the  proboscis  of  the 
flea,  as  has  been  thought  to  occur  in  the  case  of  the  plague.     To  this 


Leishmanioses  and  Insects  221 

Brumpt  objects  that  they  and  other  workers  who  thought  to  trace 
the  development  of  Leishmania  infantum  were  apparently  misled  by 
the  presence  of  a  harmless  Herpetomonas  which  infests  dog  fleas  in  all 
countries,  even  where  the  leishmaniasis  is  unknown. 

Basile  (19 10  and  191 1)  however,  carried  on  numerous  experiments 
indicating  that  the  disease  was  transferred  from  children  to  dogs 
and  from  dog  to  dog  by  the  dog  flea,  and  was  able  to  find  in  the 
tissues  of  the  insects  forms  perfectly  identical  with  those  found  in 
children  and  in  dogs  suffering  from  leishmaniasis.  He  also  found 
that  Pulex  irritans  was  capable  of  acting  as  the  carrier. 

Of  the  cutaneous  type  of  leishmaniasis,  the  best  known  is  the  so- 
called  "Oriental  sore,"  an  ulcerative  disease  of  the  skin  which  is 
epidemic  in  many  tropical  and  subtropical  regions.  The  causative 
organism  is  Leishmania  tropica,  which  occurs  in  the  diseased  tissues 
as  bodies  very  similar  to  those  found  in  the  spleen  in  cases  of 
kala-azar.  The  disease  is  readily  inoculable  and  there  is  no  doubt 
that  it  may  be  transferred  from  the  open  sores  to  abraded  surfaces  of 
a  healthy  indi\'idual  by  house-flies.  It  is  also  believed  by  a  number 
of  investigators  that  it  may  be  transferred  and  directly  inoculated 
by  various  blood-sucking  insects. 

Ticks  and  Diseases  of  Man  and  Animals 

We  ha^'e  seen  that  the  way  to  the  discoveries  of  the  relations  of 
arthropods  to  disease  was  pointed  out  by  the  work  of  Leuckart  and 
Melnikoif  on  the  life  cycle  of  Dipylidium,  and  of  Fedtschenko  and 
Manson  on  that  of  Filaria.  They  dealt  with  grosser  forms,  belonging 
to  well-recognized  parasitic  groups. 

This  was  long  before  the  role  of  any  insect  as  a  carrier  of  patho- 
genic micro-organisms  had  been  established,  and  before  the  Protozoa 
were  generally  regarded  as  of  importance  in  the  causation  of  disease. 
The  next  important  step  was  taken  in  1889  when  Smith  and  Kil- 
boume  conclusively  showed  that  the  so-called  Texas  fever  of  cattle, 
in  the  United  States,  is  due  to  an  intracorpuscular  blood  parasite 
transmitted  exclusively  by  a  tick.  This  discovery,  antedating  by 
eight  years  the  work  on  the  relation  of  the  mosquito  to  malaria,  had  a 
very  great  influence  on  subsequent  studies  along  these  lines. 

While  much  of  the  recent  work  has  dealt  with  the  true  insects, 
or  hexapods,  it  is  now  known  that  several  of  the  most  serious  diseases 
of  animals,  and  at  least  two  important  diseases  of  man  are  tick 
borne.  These  belong  to  the  types  known  collectively  as  babesioses 
(or  "  piroplasmoses") ,  and  spirochcetoses. 


22  2        Arthropods  as  Essential  Hosts  of  Pathogenic  Protozoa 

The  term  babesiosis  is  applied  to  a  disease  of  man  or  animals 
which  is  caused  by  minute  protozoan  parasites  of  the  genus  Babesia, 
living  in  the  red  blood  corpuscles.  These  parasites  have  usually  been 
given  the  generic  name  Piroplasnia  and  hence  the  type  of  disease 
which  they  cause  is  often  referred  to  as  "  piroplasmosis."  The  best 
known  illustration  is  the  disease  known  in  this  country  as  Texas 
fever  of  cattle. 

Cattle  Ticks  and  Texas  Fever — The  cattle  disease,  which  in  the 
United  States  is  known  as  Texas  fever,  is  a  widely  distributed,  exceed- 
ingly acute  disease.  In  Australia  it  is  known  as  redwater  fever  and 
in  Europe  as  haemoglobinuria,  due  to  the  fact  that  the  urine  of  the 
diseased  animals  is  discolored  by  the  breaking  down  of  the  red  blood 
corpuscles  infested  by  the  parasite. 

In  their  historical  discussion,  Smith  and  Kilboume,  point  out  that 
as  far  back  as  1796  it  was  noted  that  Southern  cattle,  in  a  state  of 
apparent  health,  might  spread  a  fatal  disease  among  Northern  herds. 
As  obser\^ations  accumulated,  it  was  learned  that  this  infection  was 
carried  only  during  the  warm  season  of  the  year  and  in  the  depth  of 
winter  Southern  cattle  were  harmless.  Moreover,  Southern  cattle 
after  remaining  for  a  short  time  in  the  North  lost  their  power  to 
transmit  the  disease,  and  the  same  was  true  of  cattle  which  had  been 
driven  for  a  considerable  distance. 

Very  significant  was  the  fact  that  the  infection  was  not  com- 
municated directly  from  the  Southern  to  Northern  cattle  but  that 
the  ground  over  which  the  former  passed  was  infected  by  them,  and 
that  the  infection  was  transmitted  thence  to  susceptible  cattle  after 
a  period  of  not  less  than  thirty  days  had  elapsed. 

Of  course  a  disease  as  striking  as  this,  and  which  caused  such 
enormous  losses  of  cattle  in  the  region  invaded  was  fruitful  in  theories 
concerning  its  causation.  The  most  widespread  was  the  belief  that 
pastures  were  infected  by  the  saliva,  urine,  or  manure  of  Southern 
cattle.  There  were  not  wanting  keen  observers  who  suggested  that 
the  disease  was  caused  by  ticks,  but  little  weight  was  given  to  their 
view. 

Various  workers  had  described  bacteria  which  they  had  isolated 
from  the  organs  of  the  diseased  animals,  but  their  findings  could  not 
be  verified.  In  1889,  Smith  and  Kilboume  discovered  a  minute, 
pear-shaped  organism  (fig.  138)  in  the  red  blood  corpuscles  of  a  cow 
which  had  succumbed  to  Texas  fever.     On  accotint  of  their  shape 


Cattle  Ticks  and  Texas  Fever 


223 


00000 
00000 


138. 


Babesia  bovis  in  blood  corpuscle? 
After  Calli. 


they  were  given  the  generic  name  Pyrososnia  and  because  they  were 
usualty  found  two  in  a  cor[3uscle,  the  specific  name,  higeminum.     It 

is  now  generally  accepted  that 
the  parasite  is  the  same  which 
Babes  had  observed  the  year 
before  in  Roumanian  cattle 
suffering  from  Hajmoglobinuria, 
and  should  be  known-as  Babesia 
bovis  (Babes). 

By  a  series  of  perfectly  con- 
clusive experiments  carried  on 
near  Washington,  D.  C,  Smith 
and  Kilboume  showed  that 
this  organism  was  carried  from  Southern  cattle  to  non-immune  ani- 
mals by  the  so-called  Southern  cattle 
tick,  Boophilus  annulatus  (=  Mar- 
gar  opus  annulatus)  (fig.  139). 

Of  fourteen  head  of  native  cattle 
placed  in  a  field  with  tick-infested 
Northern  cattle  all  but  two  contracted 
the  disease.  This  experiment  was 
repeated  with  similar  results.  Four 
head  of  native  cattle  kept  in  a  plot 
with  three  North  Carolina  cattle 
which  had  been  carefully  freed  from 
ticks  remained  healthy.  A  second 
experiment  the  same  year  gave  similar 
results. 

Still  more  conclusive  was  the  ex- 
periment showing  that  fields  which 
had  not  been  entered  by  Southern 
cattle  but  which  had  been  infected  by 
mature  ticks  taken  from  such  animals 
^^•ould  produce  Texas  fever  in  nati^"e 
cattle.  On  September  13,  1889,  sev- 
eral thousand  ticks  collected  from 
cattle  in  North  Carolina  three  and 
four  days  before,  were  scattered  in  a 

small  field  near  Washington.     Three   139.   The  cattle  tick  (Boophilus  annuiatu.s). 
out  of  four  native  animals  placed  in  comstock.''^' 


(6)    male.      After 


2  24        Arthropods  as  Essential  Hosts  of  Pathogenic  Protozoa 

this  field  contracted  the  disease.  The  fourth  animal  was  not 
examined  as  to  its  blood  but  it  showed  no  external  symptoms  of 
the  disease. 

In  these  earlier  experiments  it  was  believed  that  the  cattle  tick 
acted  as  a  carrier  of  the  disease  between  the  Southern  cattle  and  the 
soil  of  the  Northern  pastures.  "It  was  believed  that  the  tick  ob- 
tained the  parasite  from  the  blood  of  its  host  and  in  its  dissolution 
on  the  pasture  a  certain  resistant  spore  form  was  set  free  which 
produced  the  disease  when  taken  in  with  the  food."  The  feeding  of 
one  animal  for  some  time  with  grass  from  the  most  abundantly 


.//idanad 


Chi  tmize-d  points 

140.     Hyalomma  aegypticum.     After  Xuttall  and  Warburton. 

infected  field,  without  any  appearance  of  the  disease,  made  this 
hypothesis  untenable. 

In  the  experimental  work  in  1890  the  astonishing  fact  was  brought 
out  that  the  disease  was  conveyed  neither  by  infected  ticks  dis- 
integrating nor  by  their  directly  transferring  the  parasite,  but  that 
it  was  conveyed  by  the  young  hatched  from  eggs  of  infected  ticks. 
In  other  words,  the  disease  was  hereditarily  transferred  to  ticks  of 
the  second  generation  and  they  alone  were  capable  of  conveying  it. 

Thus  was  explained  the  fact  that  Texas  fever  did  not  appear 
immediately  along  the  route  of  Southern  cattle  being  driven  to 
Northern  markets  but  that  after  a  certain  definite  period  it  mani- 
fested itself.  It  was  conveyed  by  the  progeny  of  ticks  which  had 
dropped  from  the  Southern  cattle  and  deposited  their  eggs  on  the 
ground. 


Cattle  Ticks  and  Texas  Fever 


225 


These  results  ha\'e  been  fully  confirmed  by  workers  in  different 
parts  of  the  world, — notably  by  Koch,  in  Africa,  and  by  Pound,  in 
Australia. 

The  disease  is  apparently  transmitted  by  Boophilus  annulatus 
alone,  in  the  United  States,  but  it,  or  an  almost  identical  disease, 
is  conve}'ed  by  Ixodes  hexagonus  in  Norway,  Ixodes  ricinus  in  Finland 
and  France  and  by  the  three  species,  Boophilus  decolor atus,  Hyalonima 
cBgypticuni  (fig.  140  and  141),  and  Hcemaphysalis  punctata  in  Africa. 
In  spite  of  the  detailed  study  which  it  has  received,  the  life  cycle 
of  Babesia  bovis  has  not  been  satisfactorily  worked  out.     The  asexual 

reproduction      in     the 
^.jh  blood  of  the  vertebrate 

host  has  been  described 
but  the  cycle  in  the  tick 
is  practically  unknown. 
More  successful 
attempts  have  been 
made  to  work  out  the  life 
cycle  of  a  related  species, 
Babesia  canis,  which 
causes  malignant  jaun- 
dice in  dogs  in  Africa 
and  parts  of  Southern 
Europe.  In  this  in- 
stance, also,  the  disease 
is  transmitted  by  heredity  to  the  ticks  of  the  second  generation. 
Yet  the  larval,  or  "seed  ticks,"  from  an  infected  female  are  not 
capable  of  con^'eying  the  disease,  but  only  the  m^mphs  and  adults. 
Still  more  complicated  is  the  condition  in  the  case  of  Babesia  ovis  of 
sheep,  which  Motas  has  shown  can  be  conveyed  solely  by  the  adult, 
sexually  mat  lire  ticks  of  the  second  generation. 

In  Babesis  canis,  Christopher  (1907)  observed  developmental 
stages  in  the  tick.  He  found  in  the  stomach  of  adult  ticks,  large 
motile  club-shaped  bodies  which  he  considered  as  ookinetes.  These 
bodies  pass  to  the  ovaries  of  the  tick  and  enter  the  eggs  where  they 
become  globular  in  form  and  probably  represent  an  oocyst.  This 
breaks  up  into  a  number  of  sporoblasts  which  enter  the  tissues  of 
the  developing  tick  and  give  rise  to  numerous  sporozoites,  which 
collect  in  the  salivary  glands  and  thence  are  transferred  to  the 
vertebrate  host.     A  number  of  other  species  of  Babesia  are  kno^um 


141. 


Hyalomma  aegypticum.      Capitulum  of  female; 
(a)  dorsal,    (6)  ventral  aspect. 


226       Arthropods  as  Essential  Hosts  of  Pathogenic  Protozoa 

to  infest  vertebrates  and  in  all  the  cases  where  the  method  has  been 
worked  out  it  has  been  found  that  the  conveyal  was  by  ticks.  We 
shall  not  consider  the  cases  more  fully  here,  as  we  are  concerned 
especially  with  the  method  of  transfer  of  human  diseases . 

Ticks  and  Rocky  Mountain  Spotted  Fever  of  Man — Ever  since 
1 8 73  there  has  been  known  in  Montana  and  Idaho  a  peculiar  febrile 
disease  of  man,  which  has  gained  the  name  of  "Rocky  Mountain 
spotted  fever."  Its  onset  is  marked  by  chills  and  fever  which  rapidly 
become  acute.  In  about  four  to  seven  days  there  appears  a  charac- 
teristic eruption  on  the  wrists,  ankles  or  back,  which  quickly  covers 
the  body. 

McClintic  (19 12)  states  that  the  disease  has  now  been  reported 
from  practically  all  of  the  Rocky  Mountain  States,  including  Arizona, 
California,  Colorado,  Idaho,  Montana,  Nevada,  Oregon,  Utah, 
Washington,  and  Wyoming.  "Although  the  disease  is  far  more 
prevalent  in  Montana  and  Idaho  than  in  any  of  the  other  States, 
its  spread  has  assiimed  such  proportions  in  the  last  decade  as  to  call 
for  the  gravest  consideration  on  the  part  of  both  the  state  and  national 
health  authorities.  In  fact,  the  disease  has  so  spread  from  state 
to  state  that  it  has  undoubtedly  become  a  very  serious  interstate 
problem  demanding  the  institution  of  measures  for  its  control  and 
suppression." 

A  peculiar  feature  of  the  Rocky  Mountain  spotted  fever  is  a 
marked  variation  in  its  severity  in  different  localities.  In  Montana, 
and  especially  in  the  famous  Bitter  Root  Valley,  from  33  per  cent  to 
75  per  cent  of  the  cases  result  fatally.  On  the  other  hand,  the  fatality 
does  not  exceed  four  per  cent  in  Idaho. 

In  1902,  Wilson  and  Chowning  reported  the  causative  organism 
of  spotted  fever  to  be  a  blood  parasite  akin  to  the  Babesia  of  Texas 
fever,  and  made  the  suggestion  that  the  disease  was  tick-borne. 
The  careful  studies  of  Stiles  (1905)  failed  to  confirm  the  supposed 
discovery  of  the  organism,  and  the  disease  is  now  generally  classed 
as  due  to  an  invisible  virus.  On  the  other  hand,  the  accumulated 
evidence  has  fully  substantiated  the  hypothesis  that  it  is  tick-borne. 

According  to  Ricketts  (1907)  the  experimental  evidence  in  sup- 
port of  this  h\^pothesis  was  first  afforded  by  Dr.  L.  P.  McCalla  and 
Dr.  H.  A.  Brereton,  in  1905.  These  investigators  transmitted  the 
disease  from  man  to  man  in  two  experiments.  "The  tick  was 
obtained  'from  the  chest  of  a  man  very  ill  with  spotted  fever'  and 


Ticks  and  Rocky  Mountain  Spotted  Fever  oj  Man  227 

'applied  to  the  arm  of  a  man  who  had  been  in  the  hospital  for  two 
months  and  a  half,  and  had  lost  both  feet  from  gangrene  due  to 
freezing.'  On  the  eighth  day  the  patient  became  very  ill  and  passed 
through  a  mild  course  of  spotted  fever,  leaving  a  characteristic 
eruption.  The  experiment  was  repeated  by  placing  the  tick  on  a 
woman's  leg  and  she  likemse  was  infected  \vith  spotted  fever." 

The  most  detailed  studies  were  those  of  the  late  Dr.  H.  T.  Ricketts, 
and  it  was  he  who  clearly  established  the  tick  hypothesis.  In  the 
summer  of  1906  he  found  that  guinea  pigs  and  monkeys  are  very 
susceptible  to  spotted  fever  and  can  readily  be  infected  by  inocula- 
tion of  blood  from  patients  suffering  from  the  disease.  This  opened 
the  way  to  experimental  work  on  tick  transmission.  A  female  tick 
was  fed  upon  an  infected  guinea  pig  for  two  days,  removed  and 
isolated  for  two  days  and  then  placed  upon  a  healthy  guinea  pig. 
After  an  incubation  period  of  three  and  a  half  days  the  experimental 
animal  contracted  a  well-marked  case  of  the  disease. 

A  similar  result  was  obtained  at  the  same  time  by  King,  and  later 
in  the  season  Ricketts  proved  that  the  male  tick  was  also  capable 
of  transmitting  the  disease.  He  foiind  that  there  was  a  very  inti- 
mate relation  of  the  virus  to  the  tick  and  that  the  transmission  must 
be  regarded  as  biological  throughout.  Ticks  remained  infective  as 
long  as  they  lived  and  would  feed  for  a  period  of  several  months.  If 
they  acquired  the  disease  in  the  larval  or  nymphal  stage  they  retained 
it  during  molting  and  were  infective  in  the  subsequent  stages.  In  a 
few  cases  the  larv^ae  from  an  infected  female  were  infective. 

The  evidence  indicated  that  the  tick  suffers  from  a  relatively 
harmless,  generalized  infection  and  the  virus  proliferates  in  its 
body.  The  disease  probably  is  transferred  through  the  salivary 
secretion  of  the  tick  since  inoculation  experiments  show  that  the 
salivars^  glands  of  the  infected  adult  contain  the  \drus. 

It  is  probable  that  in  nature  the  reservoir  of  the  virus  of  spotted 
fever  is  some  one  or  more  of  the  naXrve  small  animals.  Infected 
ticks  have  been  found  in  nature,  and  as  various  wild  animals  are 
susceptible  to  the  disease,  it  is  ob\T.ous  that  it  may  exist  among  them 
unnoticed.  Wilson  and  Chowning  suggested  that  the  ground  squir- 
rel plays  the  principal  role. 

Unfortunately,  much  confusion  exists  regarding  the  correct 
name  of  the  tick  which  normally  conveys  the  disease.  In  the  medi- 
cal literattire  it  is  usually  referred  to  as  Dermacentor  occidentalis, 
but  students  of  the  group  now  agree  that  it  is  specifically  distinct. 


2  28        Arthropods  as  Essential  Hosts  of  Pathogenic  Protozoa 

Banks  has  designated  it  as  Dermacentor  venustus  and  this  name  is 
used  in  the  pubHcations  of  the  Bureau  of  Entomology.  On  the  other 
hand,  Stiles  maintains  that  the  common  tick  of  the  Bitter  Root 
Valley,  and  the  form  which  has  been  collected  b}^  the  authors  who 
have  worked  on  Rocky  Mountain  spotted  fever  in  that  region,  is 
separable  from  D.  venustus,  and  he  has  described  it  under  the  name  of 
Dermacentor  andersoni. 

Maver  (191 1)  has  shown  experimentally  that  spotted  fever  may 
be  transmitted  by  several  different  species  of  ticks,  notably  Dermacen- 
tor marginatus,  Dermacentor  variabilis  and  Amhlyomnia  americanum. 
This  being  the  case,  the  question  of  the  exact  systematic  status  of 
the  species  experimented  upon  in  the  Bitter  Root  Valley  becomes 
less  important,  for  since  Dermacentor  occidentalis ,  Dermacentor 
venustus  and  Dermacentor  andersoni  all  readily  attack  man,  it  is 
probable  that  either  species  would  readily  disseminate  the  disease 
if  it  should  spread  into  their  range. 

Hunter  and  Bishop  (191 1)  have  emphasized  the  fact  that  in  the 
eastern  and  southern  United  States  there  occur  several  species  which 
attack  man,  and  any  one  of  which  might  transmit  the  disease  from 
animal  to  animal  and  from  animal  to  man.  The  following  species, 
they  state,  would  probably  be  of  principal  importance  in  the  Southern 
and  Eastern  States :  the  lone  star  tick  {Amhlyomma  americanum) ; 
the  American  dog  tick  {Dermacentor  variabilis) ;  and  the  gulf -coast 
tick  [Amblyomma  maculatum).  In  the  extreme  southern  portions  of 
Texas,  Amblyomma  cajennense,  is  a  common  pest  of  man. 

Since  the  evidence  all  indicates  that  Rocky  Mountain  spotted 
fever  is  transmitted  solely  by  the  tick,  and  that  some  of  the  wild 
animals  serv^e  as  reserv^oirs  of  the  \arus,  it  is  ob\4ous  that  personal 
prophylaxis  consists  in  avoiding  the  ticks  as  fully  as  possible,  and  in 
quickly  removing  those  which  do  attack.  General  measures  alono' 
the  line  of  tick  eradication  must  be  carried  out  if  the  disease  is  to  be 
controlled.  That  such  measures  are  feasible  has  been  shown  by  the 
work  which  has  been  done  in  controlling  the  tick-borne  Texas  fever 
of  cattle,  and  by  such  work  as  has  already  been  done  against  the 
spotted  fever  tick,  which  occurs  on  both  wild  and  domestic  animals. 
Detailed  consideration  of  these  mcasm-es  is  to  be  found  in  the 
publications  of  the  Public  Health  and  Marine  Hospital  Service, 
and  the  Bureau  of  Entomolog}'.  Hunter  and  Bishopp  give  the 
following  summarized  recommendations  for  control  or  eradication 
measures  in  the  Bitter  Root  Valley. 


Ticks  and  Rocky  Mountain  Spatted  Fever  oj  Man  229 

(i)  A  campaign  of  education,  whereby  all  the  residents  of  the 
\'alley  A\ill  be  made  thoroughly  familiar  wdth  the  feasibility  of  the 
plan  of  eradication,  and  ^^^th  what  it  wall  mean  in  the  development  of 
the  valley. 

(2)  The  obtaining  of  legislation  to  make  it  possible  to  dip  or  oil 
all  live  stock  in  the  Bitter  Root  Valley. 

(3)  The  obtaining  of  an  accurate  census  of  the  horses,  cattle, 
sheep,  mules,  and  dogs  in  the  valle}'. 

(4)  The  construction  of  ten  or  more  dipping  vats. 

(5)  The  providing  of  materials  to  be  used  in  the  dipping  mixture. 

(6)  The  organization  of  a  corps  of  workers  to  carry  on  the  opera- 
tions. 

(7)  The  S3'stematic  dipping  of  the  horses,  cattle,  sheep,  and  dogs 
of  the  ^'alley  on  a  definite  weekly  schedule  from  approximately  March 
10  to  June  9. 

(8)  The  treatment  by  hand  of  the  animals  in  localities  remote 
from  vats,  on  the  same  schedule. 

They  estimate  that  after  three  seasons'  operations  a  very  small 
annual  expenditure  would  provide  against  reinfestation  of  the  valley 
by  the  incoming  of  cattle  from  other  places. 

Supplementary  measures  consist  in  the  killing  of  wild  mammals 
which  may  harbor  the  tick;  systematic  burning  of  the  brush  and 
debris  on  the  mountain  side;  and  in  clearing,  since  the  tick  is  seldom 
found  on  land  under  cultivation. 


CHAPTER    X 

ARTHROPODS   AS  ESSENTIAL   HOSTS   OF  PATHOGENIC   PROTOZOA 

[Continued] 

Arthropods  and   Spirochetoses  of   Man  and  Animals 

The  term  spirochaetoses  is  applied  to  diseases  of  man  or  animals 
which  are  due  to  protistan  parasites  belonging  to  the  group  of  slender, 
spiral  organisms  known  as  spirochaetes. 

There  has  been  much  discussion  concerning  the  relationship  of 
the  spirochaetes.  Formerly,  they  were  regarded  as  bacteria  closely 
related  to  the  forms  grouped  in  the  genus  Spirillum.  The  results 
of  the  detailed  study  which  the  spirochastes  have  received  in 
recent  years,  have  led  most  of  the  workers  to  consider  them  as  belong- 
ing to  the  protozoa.  The  merits  of  the  discussion  we  are  not  con- 
cerned with  here,  but  rather  with  the  fact  that  a  number  of  diseases 
caused  by  spirochastes  are  arthropod-borne.  The  better  known  of 
these  we  shall  discuss. 

African  Relapsing  Fever  of  Man^ — It  has  long  been  known  to  the 
natives  of  Africa  and  to  travelers  in  that  country,  that  the  bite  of  a 
certain  tick,  Ornithodoros  moubata,  may  be  followed  by  severe  or 
even  fatal  fever  of  the  relapsing  type.  Until  recent  years,  it  was 
supposed  that  the  effect  was  due  to  some  special  virulence  of  the  tick, 
just  as  nagana  of  cattle  was  attributed  to  the  direct  effect  of  the  bite 
of  the  tsetse-fly.  The  disease  is  commonly  known  as  "tick-fever" 
or  by  the  various  native  names  of  the  tick. 

In  1904,  Ross  and  Milne,  in  Uganda,  and  Button  and  Todd  on  the 
Congo,  discovered  that  the  cause  of  the  disease  is  a  spirochsete  which 
is  transmitted  by  the  tick.  This  organism  has  been  designated  by 
Novy  and  Knapp  as  Spirochceta  duttoni. 

Ornithodoros  moubata  (fig.  142),  the  carrier  of  African  relapsing 
fever,  or  "tick-fever,"  is  widely  distributed  in  tropical  Africa,  and 
occurs  in  great  numbers  in  the  huts  of  natives,  in  the  dust,  cracks 
and  crevices  of  the  dirt  floors,  or  the  walls.  It  feeds  voraciously 
on  man  as  well  as  upon  birds  and  mammals.  Like  others  of  the 
Argasid<2,  it  resembles  the  bed-bug  in  its  habit  of  feeding  primarily 
at  night.  Button  and  Todd  observed  that  the  larval  stage  is  under- 
gone in  the  egg  and  that  the  first  free  stage  is  that  of  the  octopod 
nymph. 

230 


African  Relapsing  Fever  of  Man 


231 


142.  Ornithodoros  moubata.  (a)  Anterior  part  of  venter;  (6)  second  stage 
nymph;  (c)  capitulum;  {d)  dorsal  and  (e)  ventral  aspect  of  female; 
(/)  ventral  aspect  of  nymph;  (g)  capitulum  of  nymph.  After  Nuttall 
and  Warburton. 


232        Arthropods  as  Essential  Hosts  of  Pathogenic  Protozoa 

The  evidence  that  the  fever  is  transmitted  by  this  tick  is  con- 
clusive. Koch  found  that  from  five  per  cent  to  fifteen  per  cent,  and 
in  some  places,  fifty  per  cent  of  the  ticks  captured,  harbored  the 
spirochaste.  The  disease  is  readily  transmitted  to  monkeys,  rats, 
mice  and  other  animals  and  the  earlier  experiments  along:  these  lines 
have  been  confirmed  by  many  workers. 

Not  only  are  the  ticks  which  have  fed  on  infected  individuals 
capable  of  conveying  the  disease  to  healthy  animals  but  they  trans- 
mit the  causative  organism  to  their  progeny.  Thus  Mollers  (1907), 
working  in  Berlin,  repeatedly  infected  monkeys  through  the  bites 
of  nymphs  which  had  been  bred  in  the  laboratory  from  infected  ticks. 
Still  more  astonishing  was  his  discovery  that  ticks  of  the  third  genera- 
tion were  infective.  In  other  words,  if  the  progeny  of  infected  ticks 
were  fed  throughout  life  on  healthy  animals,  and  on  maturity  de- 
posited eggs,  the  nymphs  which  hatched  from  these  eggs  would  still 
be  capable  of  carrying  the  infection. 

The  developmental  cycle  of  the  spirochaete  mthin  the  tick  has  not 
been  fully  worked  out,  though  the  general  conclusions  of  Leishman 
(1910)  have  been  supported  by  the  recent  works  of  Balfour  (1911 
and  19 1 2),  and  Hindle  (19 12),  on  the  life  cycle  of  spirochaetes  affect- 
ing fowls. 

SpirochcBta  duttoni  ingested  by  Ornithodoros  moubata  apparently 
disappear  within  a  few  days,  but  Leishman  believed  that  in  reality 
they  break  up  into  minute  granules  which  are  to  be  found  in  the 
alimentarv'  canal,  the  salivary  glands  and  the  Malpighian  tubes  of 
the  tick.  These  granules,  or  "coccoid  bodies,"  as  Hindle  calls  them, 
are  supposed  to  be  the  form  in  which  the  spirochsetes  infect  the  new 
host.  We  shall  see  later  that  Marchoux  and  Couvy  (19 13)  dis- 
sent wholly  from  this  interpretation. 

According  to  Leishman,  and  Hindle,  the  coccoid  bodies  are  not 
injected  into  the  vertebrate  host  with  the  sahva  of  the  tick,  as  are 
the  sporozoites  of  malaria  with  that  of  the  mosquito.  Instead,  they 
pass  out  mth  the  excrement  and  secondarily  gain  access  to  the 
wound  inflicted  by  the  tick. 

Nuttall  (191 2)  calls  attention  to  the  fact  that  the  geographical 
distribution  of  Ornithodoros  moubata  is  far  wider  than  our  present 
records  show  for  the  distribution  of  the  relapsing  fever  in  man  and 
that  there  is  every  reason  to  fear  the  extension  of  the  disease.  Huts 
where  the  ticks  occur  should  be  avoided  and  it  should  be  remembered 
that  in  infected  localities  there  is  special  danger  in  sleeping  on  the 
ground. 


European  Relapsing  Fever  233 

European  Relapsing  Fever — There  is  \Addely  distributed  in  Europe 
a  type  of  rcla])sing  fever  which  is  caused  by  SpirochcBta  recurrentis. 
It  has  long  been  supposed  that  this  disease  is  spread  by  the  bed-bug 
and  there  is  some  experimental  evidence  to  show  that  it  may  be 
conveyed  by  these  insects. 

In  1897,  Tictin  found  that  he  could  infect  monkeys  by  inoculating 
the  contents  of  bed-bugs  which  had  fed  upon  a  patient  within  forty- 
eight  hours.  Nuttall,  in  1907,  in  one  experiment  succeeded  in  trans- 
mitting Spirochceta  recurrentis  from  mouse  to  mouse  by  bites  of  bed- 
bugs. The  bugs,  thirty-five  in  number,  were  transferred  at  short 
intervals  from  one  mouse  to  another,  not  being  allowed  to  take  a 
full  meal  on  the  first,  or  infected  mouse. 

On  the  other  hand,  there  is  much  clinical  evidence  to  show  that 
the  European  relapsing  fever  like  various  other  types  of  the  disease 
is  transmitted  from  man  to  man  b}'  head  and  body  lice  (Pediculus 
humanus  and  Pediculus  corporis). 

Interesting  supplementary  evidence  is  that  of  Bayon's  observ^a- 
tions  ( 1 9 1 2 ) ,  in  Moscow.  ' '  Having  visited  the  big  municipal  night  hos- 
pitals  at  Moscow  I  soon  noticed  that  they  were  kept  with  such  scrupu- 
lous cleanliness,  disinfected  so  lavishly,  the  beds  of  iron,  the  floor  cement- 
ed, that  it  was  not  possible  for  bed-bugs  to  thrive  to  any  extent  on 
the  premises.  The  people  sleeping  there  were  allowed,  however, 
to  sleep  in  their  own  clothes.  The  introduction  of  these  model  homes 
had  not  had  any  effect  on  the  incidence  of  relapsing  fever,  for  the 
places  were  still  hot -beds  of  the  fever  during  winter.  On  the  other 
hand,  though  I  changed  my  rooms  several  times,  I  found  bugs  in 
every  successive  lodging,  and  I  was  told  in  Moscow,  this  can  hardly 
be  avoided.  Yet  no  foreigner,  or  Russian  of  the  better  class,  ever 
catches  relapsing  fever.  To  this  may  be  added  the  fact  that  when 
I  asked  for  clothes-lice  and  promised  to  pay  a  kopec  for  two,  the 
attendants  from  the  night  hostel  brought  me  next  morning  a  small 
ounce  bottle  crammed  with  Pediculus  capitis  (=  P.  humanus),  and 
Pediculus  vestimentorum  {=  P.  corporis)  collected  off  the  sleepers. 
If  relapsing  fever  were  transmitted  by  bed-bugs,  it  would  be  much 
more  disseminated  than  it  is  at  present  in  Moscow." 

Direct  experimental  evidence  of  the  agency  of  lice  in  transmitting 
relapsing  fever  is  especially  clear  in  the  case  of  a  type  of  the  disease 
prevalent  in  parts  of  North  Africa.  We  shall  consider  this  evidence 
later. 


234        Arthropods  as  Essential  Hosts  of  Pathogenic  Protozoa 

Other  Types  of  Relapsing  Fever  of  Man — In  addition  to  the  three 
types  of  human  relapsing  fever  already  referred  to,  several  others 
have  been  distinguished  and  have  been  attributed  to  distinct  species 
of  spirochastes.     The  various  spirochaetoses  of  man  are: 

African,  caused  by  5.  duttoni;  European,  caused  by  5.  recur- 
rentis;  North  African,  caused  by  5.  berhera;  East  African,  caused 
by  5.  rossi;  East  Indian,  caused  by  5.  carteri;  North  American, 
caused  by  5.  novyi;     South  American,  caused  by  5.  duttoni{?) 

Nuttall  (1912)  in  his  valuable  resume  of  the  subject,  has  em- 
phasized that  "in  view  of  the  morphological  similarity  of  the  sup- 
posedly different  species  of  spirochastes  and  their  individual  variations 
in  virulence,  we  may  well  doubt  if  any  of  the  'species'  are  valid. 
As  I  pointed  out  four  years  ago,  the  various  specific  names  given  to 
the  spirochaetes  causing  relapsing  fever  in  man  may  be  used  merely 
for  convenience  to  distinguish  strains  or  races  of  different  origin. 
They  cannot  be  regarded  as  valid  names,  in  the  sense  of  scientific 
nomenclature,  for  virulence  and  immunity  reactions  are  not  adequate 
tests  of  specificity." 

North  African  Relapsing  Fever  of  Man — The  type  of  human 
relapsing  fever  to  be  met  with  in  Algeria,  Tunis,  and  Tripoli,  is  due  to 
a  Spirochceta  which  does  not  differ  morphologically  from  Spirockceta 
duttoni,  but  which  has  been  separated  on  biological  grounds  as 
SpirochcBta  berberi. 

Experimenting  with  this  t^^pe  of  disease  in  Algeria,  Sergent  and 
Foly  (1910),  twice  succeeded  in  transmitting  it  from  man  to  monkeys 
by  inoculation  of  crushed  body  lice  and  in  two  cases  obtained  infec- 
tion of  human  subjects  who  had  received  infected  lice  under  their 
clothing  and  who  slept  under  coverings  harboring  many  of  the  lice 
which  had  fed  upon  a  patient.  Their  results  were  negative  mth 
Argas  persicus,  Cimex  lectularius,  Muse  a  domestica,  Hcematopinus 
spinulosus  and  Ceratophyllus  fasciatus.  They  found  body  lice 
associated  mth  every  case  of  relapsing  fevev  which  they  found  in 
Algeria. 

Nicolle,  Blaizot,  and  Conseil  (19 12)  showed  that  the  louse  did 
not  transmit  the  parasite  by  its  bite.  Two  or  three  hours  after  it 
has  fed  on  a  patient,  the  spirochastes  begin  to  break  up  and  finally 
they  disappear,  so  that  after  a  day,  repeated  examinations  fail  to 
reveal  them.  They  persist,  nevertheless,  in  some  unknown  form, 
for  if  the  obser\'ations  are  continued  they  reappear  in  eight  to  twelve 


SpirochcBtosis  of  Fowls  .  235 

days.  These  new  foiTns  are  virulent,  for  a  monkey  was  infected 
by  inoculating  a  single  crushed  louse  which  had  fed  on  infected  blood 
fifteen  days  before. 

Natural  infection  is  indirect.  Those  attacked  by  the  insect 
scratch,  and  in  this  act  they  excoriate  the  skin,  crush  the  lice  and 
contaminate  their  fingers.  The  least  abrasion  of  the  skin  serves  for 
the  entrance  of  the  spirochsetes.  Even  the  contact  of  the  soiled 
fingers  on  the  various  mucosa,  such  as  the  conjunctive  of  the  eye, 
is  sufficient. 

As  in  the  case  of  Spiroch<Bta  dutioni,  the  organism  is  transmitted 
hereditarily  in  the  arthropod  vector.  The  progeny  of  lice  which 
have  fed  on  infected  blood  may  themselves  be  infective. 

Spirochaetosis  of  Fowls — One  of  the  best  known  of  the  spiroch^etes 
transmitted  by  arthropods  is  Spirochasta  gallinarum,  the  cause  of  a 
very  fatal  disease  of  domestic  fowls  in  widely  separated  regions  of 
the  world.  According  to  Nuttall,  it  occurs  in  Southeastern  Europe, 
Asia,  Africa,  South  America  and  Australia. 

In  1903,  Marchoux  and  Salimbeni,  working  in  Brazil,  made  the 
first  detailed  study  of  the  disease,  and  showed  that  the  causative 
organism  is  transmitted  from  fowl  to  fowl  by  the  tick  Argas  persicus. 
They  found  that  the  ticks  remained  infective  for  at  least  five  months. 
Specimens  which  had  fed  upon  diseased  birds  in  Brazil  were  sent  to 
Nuttall  and  he  promptly  confirmed  the  experiments.  Since  that 
date  many  investigators,  notably  Balfour  and  Hindle,  have  contri- 
buted to  the  elucidating  of  the  life-cycle  of  the  parasite.  Since  it 
has  been  worked  out  more  fully  than  has  that  of  any  of  the  human 
spirochaetes,  we  present  Hindle's  diagram  (fig.  143)  and  quote  the 
brief  summary  from  his  preliminary  paper  (191 16). 

"Commencing  with  the  ordinary  parasite  in  the  blood  of  the  fowl, 
the  spirochaste  grows  until  it  reaches  a  certain  length  (i6-i9[jl)  and 
then  divides  by  transverse  division.  This  process  is  repeated,  and 
is  probably  the  only  method  of  multiplication  of  the  parasite  within 
the  blood.  When  the  spirochaetes  disappear  from  the  circulation, 
some  of  them  break  up  into  the  coccoid  bodies  which,  however, 
do  not  usually  develop  in  the  fowl.  When  the  spirochaetes  are 
ingested  by  Argas  persicus,  some  of  them  pass  through  the  gut  wall 
into  the  coelomic  fluid.  From  this  medium  they  bore  their  way  into 
the  cells  of  the  various  organs  of  the  tick  and  there  break  up  into  a 
number  of  coccoid  bodies.     These  intracellular  forms  multiply  by 


236       Arthropods  as  Essential  Hosts  of  Pathogenic  Protozoa 

ordinary  fission  in  the  cells  of  the  Malpighian  tubiiles  and  gonads. 
Some  of  the  coccoid  bodies  are  formed  in  the  Itimen  of  the  gut  and 
Malpighian  tubules.  The  result  is  that  some  of  the  coccoid  bodies 
ma}'  be  present  in  the  Malpighian  secretion  and  excrement  of  an 
infected  tick  and  when  mixed  with  the  coxal  fluid  may  gain  entry 
into  another  fowl  by  the  open  wound  caused  by  the  tick's  bite.     They 


143.     Spirochasta  gallinanun.     After  Hindle. 

then  elongate  and  redevelop  into  ordinary  spirochaetes  in  the  blood 
of  the  fowl,  and  the  cycle  may  be  repeated. 

Hindle's  account  is  clear  cut  and  circumstantial,  and  is  quite  in 
line  with  the  work  of  Balfour,  and  of  Leishman.  Radically  different 
is  the  interpretation  of  Marchoux  and  Couw  (19 13).  These  investi- 
gators maintain  that  the  granules  localized  in  the  Malpighian  tubules 
in  the  larvae  and,  in  the  adult,  also  in  the  o\ailes  and  the  genital  ducts 
of  the  male  and  female,  are  not  derived  from  spirochaetes  but  that  they 
exist    normally  in    many   acariens.     They  interpret  the  supposed 


Typhus  Fever  and  PedicuUdce  237 

disassociation  of  the  spirochtxte  into  granules  as  simply  the  first 
phase,  not  of  a  process  of  multiplication,  but  of  a  degeneration 
ending  in  the  death  of  the  parasite.  The  fragmented  chromatin 
has  lost  its  affinity  for  stains,  remaining  always  paler  than  that  of 
the  normal  spirochastes.  On  the  other  hand,  the  granules  of  Leish- 
man  stain  energetically  with  all  the  basic  stains. 

Further,  according  to  Marchoux  and  Couv^',  infection  takes 
place  without  the  emission  of  the  coxal  fluid  and  indeed,  soiling  of  the 
host  by  the  coxal  fluid  diluting  the  excrement  is  exceptional.  All 
of  the  organs  of  the  Argasid  are  invaded  b>'  the  parasites,  but  they 
pass  from  the  coelom  into  the  acini  of  the  salivary  glands  and  collect 
in  its  efferent  canal.     The  saliva  serves  as  the  vehicle  of  infection. 

Thus,  the  question  of  the  life  cycle  of  Spirochceta  gallinantni,  and 
of  spirochaetes  in  general,  is  an  open  one. 

It  should  be  noted  that  Argas  persicus,  the  carrier  of  SpirochcBta 
gallinarum,  is  a  common  pest  of  poultry  in  the  southwestern  United 
States.  Though  the  disease  has  not  been  reported  from  this  country, 
conditions  are  such  that  if  accidentally  introduced,  it  might  do  great 
damage. 

Other  Spirochaete  Diseases  of  Animals — About  a  score  of  other 
blood  inhabiting  spirochaetes  have  been  reported  as  occurring  in 
mammals,  but  little  is  known  concerning  their  life-histories.  One 
of  the  most  important  is  Spirochceta  theileri  which  produces  a  spiro- 
chaetosis  of  cattle  in  the  Transvaal.  Theiler  has  determined  that  it 
is  transmitted  by  an  Ixodid  tick,  Margaropus  decoloratus. 

Typhus  Fever  and  Pediculid^ 

Typhus  is  an  acute,  and  continued  fever,  formerly  epidemically 
prevalent  in  camps,  hospitals,  jails,  and  similar  places  where  persons 
were  crowded  together  under  insanitary  conditions.  It  is  accom- 
panied by  a  characteristic  rash,  which  gives  the  disease  the  common 
name  of  "spotted"  or  "lenticular"  fever.  The  causative  organism 
is  unknown. 

Typhus  fever  has  not  generally  been  supposed  to  occur  in  the 
United  States,  but  there  have  been  a  few  outbreaks  and  sporadic 
cases  recognized.  According  to  Anderson  and  Goldberger  (1912a), 
it  has  been  a  subject  of  speculation  among  health  authorities  why, 
in  spite  of  the  arrival  of  occasional  cases  in  this  country  and  of  many 
persons  from  endemic  foci  of  the  disease,  typhus  fever  apparently 
does  not  gain  a  foothold  in  the  United  States.     These  same  workers 


238       Arthropods  as  Essential  Hosts  of  Pathogenic  Protozoa 

showed  that  the  so-called  Brill's  disease,  studied  especially  in  New 
York  City,  is  identical  with  the  typhus  fever  of  Mexico  and  of 
Europe. 

The  conditions  under  which  the  disease  occurs  and  under  which 
it  spreads  most  rapidly  are  such  as  to  sugpest  that  it  is  carried  by 
some  parasitic  insect.  On  epidemiological  grounds  the  insects  most 
open  to  suspicion  are  the  lice,  bed-bugs  and  fleas. 

In  1909,  Nicolle,  Comte  and  Conseil,  succeeded  in  transmitting 
typhus  fever  from  infected  to  healthy  monkeys  by  means  of  the 
body  louse  {Pediculus  corporis).  Independently  of  this  work, 
Anderson  and  Goldberger  had  undertaken  work  along  this  line  in 
Mexico,  and  in  19 10  reported  two  attempts  to  transmit  the  disease 
to  monkeys  by  means  of  body  Hce.  The  first  experiment  resulted 
negatively,  but  the  second  resulted  in  a  slight  rise  in  temperature, 
and  in  view  of  later  results  it  seems  that  this  was  due  to  infection 
with  typhus. 

Shortly  after,  Ricketts  and  Wilder  (19 10)  succeeded  in  transmitt- 
ing the  disease  to  the  monkey  by  the  bite  of  body  lice  in  two  experi- 
ments, the  lice  in  one  instance  deriving  their  infection  from  a  man 
and  in  another  from  the  monkey.  Another  monkey  was  infected 
by  typhus  through  the  introduction  of  the  feces  and  abdominal 
contents  of  infested  lice  into  small  incisions.  Experiments  with 
fleas  and  bed-bugs  resulted  negatively. 

Subsequently,  Goldberger  and  Anderson  {tgiih)  indicated  that 
the  head  louse  {Pediculus  humanus)  as  well,  may  become  infected 
with  typhus.  In  an  attempt  to  transmit  typhus  fever  (Mexican 
virus)  from  man  to  monkey  by  subcutaneous  injection  of  a  saline 
suspension  of  crushed  head  lice,  the  monkeys  developed  a  typical 
febrile  reaction  with  subsequent  resistance  to  an  inoculation  of 
virulent  typhus  (Mexican)  blood.  In  one  of  the  three  experiments 
to  transmit  the  disease  from  man  to  monkey  by  means  of  the  bite 
of  the  head  louse,  the  animal  bitten  by  the  presimiably  infected  head 
lice  proved  resistant  to  two  successive  immunity  tests  with  viru- 
lent typhus  blood. 

In  1 9 10,  Ricketts  and  Wilder  reported  an  experiment  undertaken 
with  a  view  to  determining  whether  the  young  of  infected  lice  were 
themselves  infected.  Young  lice  were  reared  to  maturity  on  the 
bodies  of  typhus  patients,  so  that  if  the  eggs  were  susceptible  to 
infection  at  any  stage  of  their  development,  they  would  have  every 
opportunity  of  being  infected  %vithin  the  ovary.  The  eggs  of  these 
infected  lice  were  obtained,  they  were  incubated,  and  the  yoimg  lice 


Typhus  Fever  and  Pediculidce  239 

of  the  second  generation  were  lilaced  on  a  normal  rhesus  monkey. 
The  experimenters  were  unable  to  keep  the  monkey  under  very 
close  observ^ation  during  the  follomng  three  or  four  weeks,  but  from 
the  fact  that  he  proved  resistant  to  a  subsequent  immunity  test 
they  concluded  that  he  probably  owed  this  immunity  to  infection 
by  these  lice  of  the  second  generation. 

Anderson  and  Goldberger  (19 126)  object  that  due  consideration 
was  not  given  to  the  possibility  of  a  variable  susceptibility  of  the 
monkey  to  typhus.  Their  similar  experiment  was  "frankly  nega- 
tive." " 

Prophylaxis  against  typhus  fever  is,  therefore,  primarily  a  ques- 
tion of  vermin  extermination.  A  brief  article  by  Dr.  Goldberger 
(1914)  so  clearly  shows  the  practical  application  of  his  work  and  that 
of  the  other  investigators  of  the  subject,  that  we  abstract  from  it 
the  f ollo^^dng  accotmt : 

"In  general  terms  it  may  be  stated  that  association  with  a  case  of 
typhus  fever  in  the  absence  of  the  transmitting  insect  is  no  more 
dangerous  than  is  association  with  a  case  of  yellow  fever  in  the 
absence  of  the  yellow  fever  mosquito.  Danger  threatens  only  when 
the  insect  appears  on  the  scene." 

"We  may  say,  therefore,  that  to  prevent  infection  of  the  indi- 
\ddual  it  is  necessary  for  him  only  to  avoid  being  bitten  by  the  louse. 
In  theory  this  may  readily  be  done,  for  we  know  that  the  body  louse 
infests  and  attaches  itself  almost  entirely  to  the  body  linen,  and  that 
boiling  kills  this  insect  and  its  eggs.  Individual  prophylaxis  is 
based  essentially,  therefore,  on  the  avoidance  of  contact  with  indi- 
^^duals  likely  to  harbor  lice.  Practically,  however,  this  is  not 
always  as  easy  as  it  may  seem,  especially  under  the  conditions  of 
such  intimate  association  as  is  imposed  by  urban  life.  Particiilarly 
is  this  the  case  in  places  such  as  some  ol  the  large  Mexican  cities, 
where  a  large  proportion  of  the  population  harbors  this  vermin. 
Under  such  circumstances  it  is  well  to  avoid  crowds  or  crowded  places, 
such  as  public  markets,  crowded  streets,  or  public  assemblies  at 
which  the  'peon'   gathers." 

"Community  prophylaxis  efficiently  and  intelligently  carried  out 
is,  from  a  certain  point  of  view,  probably  easier  and  more  eiTective 
in  protecting  the  individual  than  is  the  individual's  own  eflfort  to 
guard  himself.  Typhus  emphasizes,  perhaps  better  than  any  other 
disease,  the  fact  that  fundamentally,  sanitation  and  health  are 
economic  problems.  In  proportion  as  the  economic  condition  of  the 
masses  has  improved — that  is,  in  proportion  as  they  could  afford 


240        Arthropods  as  Essential  Hosts  of  Pathogenic  Protozoa 

to  keep  clean — the  notorious  filth  disease  has  decreased  or  dis- 
appeared. In  localities  where  it  still  prevails,  its  further  reduction 
or  complete  eradication  waits  on  a  further  improvement  in,  or  exten- 
sion of,  the  improved  economic  status  of  those  afflicted.  Economic 
evolution  is  very  slow  process,  and,  while  doing  what  we  can  to  hasten 
it,  we  must  take  such  precautions  as  existing  conditions  permit, 
looking  to  a  reduction  in  or  complete  eradication  of  the  disease." 

"When  possible,  public  bath  houses  and  public  wash  houses, 
where  the  poor  may  bathe  and  do  their  washings  at  a  minimum  or 
without  cost,  should  be  proAnded.  Similar  provision  should  be 
made  in  military  and  construction  camps.  Troops  in  the  field  should 
be  given  the  opportunity  as  frequently  as  possible  to  wash  and  scald 
or  boil  their  body  linen." 

"Lodging  houses,  cheap  boarding  houses,  night  shelters,  hospitals, 
jails  and  prisons,  are  important  factors  in  the  spread  and  frequently 
constitute  foci  of  the  disease.  They  should  receive  rigid  sanitary 
super\nsion,  including  the  enforcement  of  measures  to  free  all  inmates 
of  such  institutions  of  lice  on  admission." 

"So  far  as  individual  foci  of  the  disease  are  concerned  these 
should  be  dealt  with  by  segregating  and  keeping  under  observation 
all  exposed  individuals  for  14  da^'s — the  period  of  incubation — from 
the  last  exposure,  by  disinfecting  (boiling  or  steaming)  the  suspected 
bedding,  body  linen,  and  clothes,  for  the  destruction  of  any  possible 
\^ermin  that  they  may  harbor,  and  by  fiunigating  (wdth  sulphur) 
the  quarters  that  they  may  have  occupied." 

"It  vnW  be  noted  that  nothing  has  been  said  as  to  the  disposition 
of  the  patient.  So  far  as  the  patient  is  concerned,  he  should  be 
removed  to  'clean'  surroundings,  making  sure  that  he  does  not 
take  with  him  any  vermin.  This  may  be  done  by  bathing,  treating 
the  hair  ^\^th  an  insecticide  (coal  oil,  tincture  of  larkspur),  and  a 
complete  change  of  body  linen.  Aside  from  this,  the  patient  may 
be  treated  or  cared  for  in  a  general  hospital  ward  or  in  a  private  house, 
pro^^ded  the  sanitary  officer  is  satisfied  that  the  new  surroundings 
to  which  the  patient  has  been  removed  are  'clean,'  that  is,  free 
from  vermin.  Indeed,  it  is  reasonably  safe  to  permit  a  'clean' 
patient  to  remain  in  his  own  home  if  this  is  'clean,'  for,  as  has  al- 
ready been  emphasized,  there  can  be  no  spread  in  the  absence  of  lice. 
This  is  a  common  experience  in  native  families  of  the  better  class 
and  of  Europeans  in  Mexico  City." 

"Similarly  the  sulphur  fumigation  above  prescribed  may  be 
dispensed  with  as  unnecessary  in  this  class  of  cases." 


CHAPTER  XI 

SOME  POSSIBLE,  BUT  IMPERFECTLY  ESTABLISHED  CASES  OF 
ARTHROPOD  TRANSMISSION  OF  DISEASE 

Infantile  Paralysis  or  Acute  Anterior  Poliomyelitis 

The  disease  usuall}'  known  in  this  country  as  infantile  paralysis 
or,  more  technically,  as  acute  anterior  poliomyelitis,  is  one  which 
has  aroused  much  attention  in  recent  years. 

The  causative  organism  of  infantile  paralysis  is  unknown,  but 
it  has  been  demonstrated  that  it  belongs  to  the  group  of  filterable 
viruses.  It  gives  rise  to  a  general  infection,  producing  characteristic 
lesions  in  the  central  nervous  system.  The  result  of  the  injury  to 
the  motor  nerves  is  a  more  or  less  complete  paralysis  of  the  corres- 
ponding muscle.  This  usually  manifests  itself  in  the  legs  and  arms. 
The  fatal  cases  are  usually  the  result  of  paralysis  of  the  muscles 
of  respiration.  Of  the  non-fatal  cases  about  60  per  cent  remain 
permanently  crippled  in  varying  degrees. 

Though  long  known,  it  was  not  until  about  i8go  that  it  was 
emphasized  that  the  disease  occurs  in  epidemic  form.  At  this  time 
Medin  reported  his  observations  on  an  epidemic  of  forty-three  cases 
which  occurred  in  and  around  Stockholm  in  1887.  Since  then, 
according  to  Frost  ( 1 9 1 1 ) ,  epidemics  have  been  observed  with  increas- 
ing frequency  in  various  parts  of  the  world.  The  largest  recorded 
epidemics  have  been  those  in  Vermont,  1894,  126  cases;  Norway  and 
Sweden,  1905,  about  1,500  cases;  New  York  City,  1907,  about 
2,500  cases.  Since  1907  many  epidemics  have  been  reported  in  the 
United  States,  and  especially  in  the  Northern  States  east  of  the 
Dakotas.  In  19 12  there  were  over  300  cases  of  the  disease  in  Buffalo, 
N.  Y.,  with  a  mortality  of  somewhat  over  11  per  cent. 

In  \n.e\v  of  the  sudden  prominence  and  the  alarming  spread  of 
infantile  paralysis,  there  have  been  many  attempts  to  determine 
the  cause,  and  the  manner  in  which  the  disease  spreads  and  develops 
in  epidemic  form.  In  the  course  of  these  studies,  the  question  of 
possible  transmission  by  insects  was  naturally  suggested. 

C.  W.  Howard  and  Clark  (19 12)  presented  the  results  of  studies 
in  this  phase  of  the  subject.  They  dealt  especially  ^^nth  the  house- 
fly, bedbug,  head,  and  body  lice,  and  mosquitoes.  It  was  found 
that  the  house-fly  (Musca  domestica)  can  carry  the  \arus  of  poliom3'e- 
litis  in  an  active  state  for  several  days  upon  the  surface  of  the  body 

241 


242  Arthropod  Transmission  of  Disease 

and  for  several  hours  within  the  gastro-intestinal  tract.  Mosquitoes 
and  lice  were  found  not  to  take  up  or  maintain  the  virus.  On  the 
other  hand,  the  bedbug  (Cimex  lectularius)  was  found  to  take  the 
\-irus  from  the  infected  monkeys  and  to  maintain  it  in  a  living  state 
within  the  body  for  a  period  of  seven  days.  This  was  demonstrated 
b}'  grinding  up  in  salt  solution,  insects  which  had  fed  on  poliomyeletic 
animals  and  injecting  the  filtrate  into  a  healthy  monkey.  The  experi- 
menters doubted  that  the  bedbug  is  a  carrier  of  the  virus  in  nature. 

Earlier  in  the  same  year,  Brues  and  Sheppard  published  the  results 
of  an  intensive  epidemiological  study  of  the  outbreak  of  191 1,  in 
Massachusetts.  Special  attention  had  been  paid  to  the  possibility 
of  insect  transfer  and  the  following  conclusion  was  reached: 

' '  Field  work  during  the  past  summer  together  with  a  consideration 
of  the  epidemiology  of  the  disease  so  far  as  known,  points  strongly 
toward  biting  flies  as  possible  carriers  of  the  \nras.  It  seems  probable 
that  the  common  stable-fly  {Stomoxys  calcitrans  L.)  may  be  responsi- 
ble to  a  certain  extent  for  the  spread  of  acute  epidemic  poliomyelitis, 
possibly  aided  by  other  biting  flies,  such  as  Tabanus  lineola.  No 
facts  which  disprove  such  a  hypothesis  have  as  yet  been  adduced, 
and  experiments  based  upon  it  are  now  in  progress." 

As  stated  by  Brues  (19 13),  especial  suspicion  fell  upon  the  stable- 
fly  because : 

1 .  The  blood-sucking  habits  of  the  adult  fly  suit  it  for  the  transfer 
of  virus  present  in  the  blood. 

2.  The  seasonal  abundance  of  the  fly  is  ver}"  closely  correlated 
with  the  incidence  of  the  disease,  rising  rapidly  during  the  summer 
and  reaching  a  maximum  in  July  and  August,  then  slowly  declining 
in  September  and  October. 

3.  The  geographical  distribution  of  the  fly  is,  so  far  as  can  be 
ascertained,  wider,  or  at  least  co-extensive  with  that  of  poliomyelitis. 

4.  Stomoxys  is  distinctly  more  abundant  under  rural  conditions, 
than  in  cities  and  thickly  popiilated  areas. 

5.  While  the  disease  spreads  over  districts  quickly  and  in  a 
rather  erratic  way,  it  often  appears  to  follow  along  lines  of  travel, 
and  it  is  known  that  Stomoxys  flies  will  often  follow  horses  for  long 
distances  along  highways. 

6.  In  a  surprisingly  large  number  of  cases,  it  appeared  probable 
that  the  children  affected  had  been  in  the  habit  of  frequenting  places 
where  Stomoxys  is  particularly  abundant,  i.e.,  about  stables,  barn- 
yards, etc. 


Infantile  Paralysis  or  Acute  Anterior  Poliomyelites  243 

The  experiments  referred  to  were  carried  on  during  the  summer  of 
191 2  and  in  September  Dr.  Rosenau  announced  that  the  disease  was 
transferred  by  the  bite  of  the  stable-fly. 

A  monkey  infected  by  inoculation  was  exposed  to  the  bites  of 
upwards  of  a  thousand  of  the  Stomoxys  flies  daily,  by  stretching  it 
at  full  length  and  rolling  it  in  a  piece  of  chicken  wire,  and  then  placing 
it  on  the  floor  of  the  cage  in  which  the  flies  were  confined.  The  flies 
fed  freely  from  the  first,  as  well  as  later,  after  paralysis  had  set  in. 
Alternating  ^^dth  the  inoculated  monkey,  healthy  monkeys  were 
similarly  introduced  into  the  cage  at  intervals.  New  monkeys  were 
inoculated  to  keep  a  supply  of  such  infected  animals  and  additional 
healthy  ones  were  exposed  to  the  flies,  which  fed  willingly  and  in 
considerable  numbers  on  each  occasion.  "Thus  the  flies  were  given 
ever\^  opportunity  to  obtain  infection  from  the  monkeys,  since  the 
animals  were  bitten  during  practically  every  stage  of  the  disease 
from  the  time  of  the  inoculation  of  the  virus  till  their  death  follow- 
ing the  appearance  of  paralysis.  Ba'  the  same  arrangement  the 
healthy  monkeys  were  likely  to  be  bitten  by  flies  that  had  previously 
fed  during  the  various  stages  of  the  disease  on  the  infected  monkeys. 
The  flies  had  meanwhile  enjoyed  the  opportunity  of  incubating  the 
\4nis  for  periods  var\4ng  from  the  day  or  two  which  usually  elapses 
between  consecutive  feedings,  to  the  two  or  three-week  period  for 
which  at  least  some  (although  a  very  small  percentage)  of  the  flies 
lived  in  the  cage." 

"In  all,  twelve  apparently  healthy  monkeys  of  a  small  Japan 
species  were  exposed  to  the  flies  in  the  manner  described  for  the  in- 
fected monkeys.  Some  were  placed  in  the  cage  only  once  or  twice 
and  others  a  number  of  times  after  varying  intervals.  These  ex- 
posures usually  lasted  for  about  half  an  hour,  but  were  sometimes 
more  protracted.  No  results  were  apparent  until  two  or  three 
weeks  after  the  experiment  was  well  under  way,  and  then  in  rather 
rapid  succession  six  of  the  animals  developed  symptoms  of  poliomye- 
litis. In  three,  the  disease  appeared  in  a  virulent  form,  resulting 
in  death,  while  the  other  three  experienced  transient  tremblings, 
diarrhoea,  partial  paralysis  and  recovery." — Brues,  19 13. 

Ver\^  soon  after  the  announcement  of  the  results  of  experiments 
by  Rosenau  and  Brues,  they  were  apparently  conclusively  confirmed 
by  Anderson  and  Frost  (19 12),  who  repeated  the  experiments,  at 
Washington.  They  announced  that  through  the  bites  of  the  Stomoxys 
flies  that  had  previously  fed  on  infected  monkeys,  they  had  succeeded 
in  experimentally  infecting  three  healthy  monkeys. 


244  Arthropod  Transmission  of  Disease 

The  results  of  these  experiments  gained  much  pubHcity  and  in 
spite  of  the  conservative  manner  in  which  they  had  been  announced, 
it  was  widely  proclaimed  that  infantile  paralysis  was  conveyed  in 
nature  by  the  stable-fly  and  by  it  alone. 

Serious  doubt  was  cast  on  this  theory  by  the  results  of  further 
experiments  by  Anderson  and  Frost,  reported  in  May  of  19 13. 
Contrary  to  the  expectations  justified  by  their  first  experience,  the 
results  of  all  the  later,  and  more  extended,  experiments  were  wholly 
negative.  Not  once  were  these  investigators  again  able  to  transmit 
the  infection  of  poliomyelitis  through  Stomoxys.  They  concluded  that 
it  was  extremely  doubtful  that  the  insect  was  an  important  factor 
in  the  natural  transmission  of  the  disease,  not  only  because  of  their 
series  of  negative  results,  "but  also  because  recent  experiments  have 
afforded  additional  evidence  of  the  direct  transmissibility  or  con- 
tagiousness of  poliomyelitis,  and  because  epidemiological  studies 
appear  to  us  to  indicate  that  the  disease  is  more  likely  transmitted 
largely  through  passive  human  virus  carriers." 

Soon  after  this,  Kling  and  Levaditi  (1913)  published  their  detailed 
studies  on  acute  anterior  poliomyelitis.  They  considered  that  the 
experiments  of  Flexner  and  Clark  (and  Howard  and  Clark),  who  fed 
house-flies  on  emulsion  of  infected  spinal  cord,  were  under  conditions 
so  different  from  what  could  occur  in  nature  that  one  cotild  not 
draw  precise  conclusions  from  them  regarding  the  epidemiology  of 
the  disease.  They  cited  the  experiments  of  Josef  son  (19 12),  as 
being  under  more  reasonable  conditions.  He  sought  to  determine 
whether  the  inoculation  of  monkeys  with  flies  caught  in  the  wards  of 
the  Hospital  for  Contagious  Diseases  at  Stockholm,  where  they  had 
been  in  contact  with  cases  of  poliomyelitis,  would  produce  the 
disease.     The  results  were  completely  negative. 

Kling  and  Lavaditi  made  four  attempts  of  this  kind.  The  flies 
were  collected  in  places  where  poliomyelitics  had  dwelt,  three,  four 
and  twenty -four  after  the  beginning  of  the  disease  in  the  family  and 
one,  three,  and  fifteen  days  after  the  patient  had  left  the  house. 
These  insects  were  for  the  greater  part  living  and  had  certainly  been 
in  contact  with  the  infected  person.  In  addition,  flies  were  used 
which  had  been  caught  in  the  wards  of  the  Hospital  for  Contagious 
Diseases  at  Soderkoping,  when  numbers  of  poliomyelitics  were  con- 
fined there.  Finally,  to  make  the  conditions  as  favorable  as  possible, 
the  emulsions  prepared  from  these  flies  were  injected  without  previous 
filtering,  since  filtration  often  causes  a  weakening  of  the  virus.     In 


Infantile  Paralysis  or  Acute  Anterior  Poliomyelitis  245 

spite  of  these  precautions,  all  their  results  were  negative,  none  of  the 
inoculated  animals  having  contracted  poliomyelitis.  They  also 
experimented  ^vith  bedbugs  which  had  fed  upon  infected  ]3atients  at 
various  stages  of  the  disease,  but  the  results  in  these  cases  also  were 
wholly  negative. 

Kling  and  Levaditi  considered  at  length  the  possibility  of  trans- 
mission of  the  disease  by  Stonioxys.  As  a  result  of  their  epidemiologi- 
cal studies,  they  found  that  infantile  paralysis  continued  to  spread 
in  epidemic  form  in  the  dead  of  ^^dnter,  when  these  flies  were  very 
rare  and  tori^id,  or  were  even  completely  absent.  Numerous  cases 
developed  in  the  northern  part  of  Sweden  late  in  October  and 
November,  long  after  snow  had  fallen.  On  account  of  the  rarity 
of  the  Stomoxys  flies  during  the  period  of  their  investigations  they 
were  unable  to  conduct  satisfactory  experiments.  In  one  instance, 
during  a  severe  epidemic,  they  found  a  number  of  the  flies  in  a  stable 
near  a  house  inhabited  by  an  infected  family,  though  none  was 
found  in  the  house  itself.  These  flies  were  used  in  preparing  an 
emulsion  which,  after  filtering,  was  injected  into  the  peritoneal 
cavity  of  a  monkey.     The  result  was  wholly  negative. 

As  for  the  earlier  experiments,  Kling  and  Levaditi  believe  if  the 
flies  were  responsible  for  the  transmission  of  the  disease  in  the  cases 
reported  by  Rosenau  and  Brues.  and  the  first  experiments  of  Ander- 
son and  Frost,  it  was  because  the  virus  of  infantile  paralysis  is  elimi- 
nated ^^dth  the  nasal  secretions  of  paralyzed  monkeys  and  the  flies, 
becoming  contaminated,  had  merely  acted  as  accidental  carriers. 

Still  further  evidence  against  the  hypothesis  of  the  transmission 
of  acute  anterior  poliomyelitis  by  Stomoxys  calcitrans  was  brought 
forward  by  Sawyer  and  Herms  (19 13).  Special  precautions  were 
used  to  prevent  the  transference  of  sali\'a  or  other  possibly  infectious 
material  from  the  surface  of  one  monkey  to  that  of  another,  and  to 
avoid  the  possibility  of  complicating  the  experiments  by  intro- 
ducing other  pathogenic  organisms  from  wild  flies,  only  laboratory- 
bred  flies  were  used.  In  a  series  of  seven  carefully  performed  experi- 
ments, in  which  the  conditions  were  varied,  Sam^er  and  Herms  were 
unable  to  transmit  poliomyelitis  from  monkey  to  monkey  through 
the  agency  of  Sto-inoxySy  or  to  obtain  any  indication  that  the  fly  is  the 
usual  agent  for  spreading  the  disease  in  nature. 

The  evidence  at  hand  to  date  indicates  that  acute  anterior  polio- 
myelitis, or  infantile  paralysis,  is  transmitted  by  contact  with  in- 
fected persons.  Under  certain  conditions  insects  may  be  agents  in 
spreading  the  disease,  but  their  role  is  a  subordinate  one. 


246 


Arthropod  Transmission  of  Disease 


Pellagra 
Pellagra  is  an  endemic  and  epidemic  disease  characterized  by  a 
peculiar  eruption  or  erj'thema  of  the  skin  (figs  144  and  145),  digestive 

disturbances  and  nerv'^ous  trouble. 
Insanity  is  a  common  result,  rather 
than  a  precursor  of  the  disease. 
The  manifestations  of  pellagra  are 
periodic  and  its  duration  indeter- 
minate. 

The  disease  is  one  the  very  name 
of  which  was  almost  unknown  in  the 
United  States  until  ^vithin  the  past 
decade.  It  has  usually  been  regarded 
as  tropical,  though  it  occurs  commonly 
in  Italy  and  in  various  parts  of  Europe. 
Now  it  is  known  that  it  not  only 
occurs  quite  generally  in  the  United 
States  but  that  it  is  spreading.  Lav- 
inder  (191 1)  says  that  "There  are 
certainly  many  thousand  cases  of  the 
disease  in  this  country',  and  the  pres- 
ent situation  must  be  looked  upon 
with  grave  concern." 
It  is  not  within  the  scope  of  this  book  to  undertake  a  general 
discussion  of  pellagra.  The  subject  is  of  such  importance  to  every 
medical  man  that  we  cannot  do  better  than  refer  to  Lavinder's 
valuable  precis.  We  can  only  touch  briefly  upon  the  entomological 
phases  of  the  problems  presented. 

The  most  commonly  accepted  theories  regarding  the  etiology 
of  the  disease  have  attributed  it  to  the  use  of  Indian  com  as  an  article 
of  diet.  This  supposed  relationship  was  explained  either  on  the 
basis  of,  (a)  insufficiency^  of  nutriment  and  inappropriateness  of 
com  as  a  prime  article  of  food ;  (b)  toxicity  of  com  or,  (c)  parasitism 
of  certain  organisms — fungi  or  bacteria^ngested  with  either  sound 
or  deteriorated  com. 

In  1905,  Sambon  proposed  the  theory  of  the  protozoal  origin  of 
pellagra  and  in  19 10  he  marshalled  an  imposing  array  of  objections 
to  the  theor}^  that  there  existed  any  relationship  between  com  and 
the  disease.  He  presented  clear  ev'idence  that  pellagra  existed  in 
Europe  before  the  introduction  of  Indian  corn  from  America,  as  an 


Pellagrous  eruption  on  the  face. 
After  Watson. 


Pellagra 


247 


article  of  diet,  and  that  its  spread  was  not  pari  passu  with  that  of  the 
use  of  com.  Cases  were  found  in  which  the  patients  had  apparently 
never  used  com,  though  that  is  obviously  difficult  to  establish.  He 
showed  that  preventive  measures  based  on  the  theory  had  been  a 
failure.  Finally,  he  believed  that  the  recurrence  of  symptoms  of 
the  disease  for  successive  springs,  in  patients  who  abstained  absolutely 
from  the  use  of  corn,  militated  against  the  theory. 

On  the  other  hand,  Sambon  believed  that  the  periodicity  of  the 
symptoms,  peculiarities  of  distribution  and  seasonal  incidence,  and 
analogies  of  the  symptoms  to  those  of  other  i^arasitic  diseases  indi- 


145.      Pellagrous  eruption  on  the  hand.      After  Watson. 

cated  that  pellagra  was  of  protozoal  origin,  and  that  it  was  insect- 
borne. 

The  insect  carriers,  he  believed  to  be  one  or  more  species  of 
Simuliidse,  or  black-flies.  In  support  of  this  he  stated  that  SimuUum 
appears  to  effect  the  same  topographical  conditions  as  pellagra, 
that  in  its  imago  stage  it  seems  to  present  the  same  seasonal  incidence, 
that  it  has  a  wide  geographical  distribution  which  seems  to  cover 
that  of  pellagra,  and  that  species  of  the  genus  are  known  to  cause 
severe  epizootics.  Concluding  from  his  studies  in  Italy,  that  pel- 
lagra was  limited  almost  wholh'  to  agricultural  laborers,  he  pointed 
out  that  the  Simulium  flies  are  found  only  in  rural  districts,  and  as  a 
rule  do  not  enter  towns,  villages,  or  houses. 

When  Sambon's  detailed  report  was  published  in  19 10,  his  theory 
was  seized  upon  e^•er>'whcre  by  workers  who  were  anxious  to  test  it 


Arthropod  Transmission  of  Disease 


146.     A  favorite  breeding  place  of  Simulium.     Ithaca,  N.  Y. 


Pellagra  249 

and  who,  in  most  cases,  were  favorably  disposed  towards  it  because 
of  the  wonderful  progress  which  had  been  made  in  the  understanding 
of  other  insect-borne  diseases.  In  this  country,  the  entomological 
aspects  of  the  subject  have  been  dealt  with  especially  by  Forbes 
(19 1 2),  and  by  King  and  Jennings,  under  the  direction  of  W.  D. 
Hunter,  of  the  Bureau  of  Entomology,  and  in  co-operation  with 
the  Thompson- McFadden  Pellagra  Commission  of  the  Department 
of  Tropical  Medicine  of  the  New  York  Post-Graduate  Medical 
School.  An  important  series  of  experiments  with  monkeys  has 
been  undertaken  by  S.J.  Hunter,  of  Kansas,  but  unfortunately  we  have 
as  yet  no  satisfactory  evidence  that  these  animals  are  susceptible 
to  the  disease — a  fact  which  renders  the  whole  problem  difficult. 

The  accumulated  evidence  is  increasingly  opposed  to  Sambon's 
hypothesis  of  the  transmission  of  pellagra  by  Simulium.  This  has 
been  so  clearly  manifested  in  the  work  of  the  Thompson-McFadden 
Commission  that  we  quote  here  from  the  report  by  Jennings  (1914) : 

"Our  studies  in  19 12  convinced  us  that  there  was  little  evidence 
to  support  the  incrimination  of  any  species  of  Simulium  in  South 
Carolina  in  the  transmission  of  pellagra.  Reviewing  the  group  as  a 
whole,  we  find  that  its  species  are  essentially  "wild"  and  lack  those 
habits  of  intimate  association  with  man  which  would  be  expected 
in  the  vector  of  such  a  disease  as  pellagra.  Although  these  flies  are 
excessively  abundant  in  some  parts  of  their  range  and  are  moderately 
so  in  Spartanburg  County,  man  is  merely  an  incidental  host,  and  no 
disposition  whatever  to  seek  him  out  or  to  invade  his  domicile  seems 
to  be  manifested.  Critically  considered,  it  is  nearer  the  fact  that 
usually  man  is  attacked  only  when  he  invades  their  habitat." 

"As  our  knowledge  of  pellagra  accumulates,  it  is  more  and  more 
evident  that  its  origin  is  in  some  way  closely  associated  with  the 
domicile.  The  possibility  that  an  insect  whose  association  with  man 
and  his  immediate  environment  is,  at  the  best,  casual  and  desultory, 
can  be  active  in  the  causation  of  the  disease  becomes  increasingly 
remote." 

"Our  knowledge  of  the  biting  habits  of  Simulium  is  not  complete, 
but  it  is  evident,  as  regards  American  species  at  least,  that  these  are 
sometimes  not  constant  for  the  same  species  in  different  localities. 
Certain  species  will  bite  man  freely  when  opportunity  offers,  while 
others  have  never  been  known  to  attack  him.  To  assimie  that  the 
proximity  of  a  Simulium-hree6m.g  stream  necessarily  implies  that 
persons  in  its  vicinity  must  be  attacked    and  bitten  is  highly  fal- 


250  Arthropod  Transmission  of  Disease 

lacious.  In  Spartanburg  County  attacks  by  Simuliuni  seems  to  be 
confined  to  the  immediate  vicinity  of  the  breeding -places.  Our 
records  and  observations,  exceedingly  few  in  number,  refer  almost 
exclusively  to  such  locations.  Statements  regarding  such  attacks, 
secured  with  much  care  and  discrimination  from  a  large  number  of 
persons,  including  many  pellagrins,  indicate  conclusively  that  these 
insects  are  seldom  a  pest  of  man  in  this  county.  A  certain  number 
of  the  persons  questioned  were  familiar  with  the  gnats  in  other 
localities,  but  the  majority  were  seemingly  ignorant  of  the  existence 
of  such  flies  with  biting  habits.  This  is  especially  striking,  in  view 
of  the  fact  that  the  average  distance  of  streams  from  the  homes  of 
the  pellagra  cases  studied  was  about  200  yards,  many  being  at  a 
distance  of  less  than  100  yards,  and  that  78  per  cent  of  these  streams 
were  found  to  be  infested  by  larval  Simulium.  Such  ignorance  in  a 
large  number  of  persons  cannot  be  overlooked  and  indicates  strongly 
that  our  belief  in  the  negligible  character  of  local  attacks  by  Simulium 
is  well  founded." 

"In  localities  infested  by  'sand-flies,'  mosquitoes,  etc.,  these 
pests  are  always  well  kno\\TL  and  the  ignorance  described  above  is 
very  significant." 

"Such  positive  reports  as  we  received  nearly  always  referred  to 
bites  received  in  the  open,  along  streams,  etc.,  and  observations  made 
of  their  attack  were  of  those  on  field  laborers  in  similar  situations. 
Males  engaged  in  agricultural  pursuits  are  almost  exempt  from 
pellagra  in  Spartanburg  County.  During  the  season  of  19 13,  in 
some  two  or  three  instances,  observations  were  made  of  the  biting 
of  Simulium  and  some  additional  and  entirely  creditable  reports 
were  received.  These  obser\'ations  and  reports  were  under  condi- 
tions identical  with  those  referred  to  in  the  reports  of  191 2  and  con- 
firm the  conclusions  based  on  the  observations  of  that  year.  I 
would  repeat  with  emphasis  that  it  is  inconceivable  that  a  fly  of  the 
appearance  and  habits  of  the  prevalent  species  of  Simulium  could  be 
present  in  such  a  region,  especially  about  the  haunts  of  man  and 
attack  him  with  s\ifficient  frequency  and  regularity  to  satisfactorily 
account  for  so  active  and  pre^'alent  a  disease  as  pellagra  without 
being  a  well-known  and  recognized  pest." 

"In  connection  with  the  conditions  in  the  Piedmont  region  of 
South  Carolina,  it  may  be  well  to  cite  the  results  of  a  study  of  those 
in  the  arid  region  of  western  Texas." 


Pellagra  251 

"In  May,  1913,  in  company  with  Capt.  J.  F.  Silcr  of  the  Thomp- 
son-IMcFadden  Pellagra  Commission,  I  visited  the  region  of  which 
Midland  in  Midland  County  is  the  center.  This  region  is  very  dry 
and  totalh'  de^'oid  of  lomning  water  for  a  long  distance  in  every 
direction.  The  only  natural  source  of  water-su]3ply,  a  few  water 
holes  and  ijonds,  were  visited  and  found  to  be  of  such  a  nature  that 
the  survival  of  Simulium,  far  less  its  ])ropagation  in  them,  is  abso- 
lutely impossible.  The  nearest  stream  affording  possibilities  as  a 
source  of  Simulium  is  60  miles  away,  while  the  average  distance  of 
such  possibility  is  not  less  than  100  miles." 

"Artificial  sources  of  water-supply  were  also  investigated  care- 
fully and  were  found  to  offer  no  o])]Jortvinity  for  the  breeding  of 
Simulium." 

"At  Midland  the  histories  of  five  cases  of  pellagra  were  obtained, 
which  gave  clear  evidence  that  this  place  or  its  immediate  vicinity 
was  the  point  of  origin.  Persons  of  long  residence  in  the  country 
were  questioned  as  to  the  occurrence  of  such  fiies  as  Simulium  and 
returned  negative  answers.  These  included  a  retired  cattle  owner, 
who  is  a  man  of  education  and  a  keen  observer,  an  expert  veterinarian 
stationed  in  the  country  who  has  the  cattle  of  the  country  under 
constant  observation,  and  a  practical  cattle  man,  manager  of  a  ranch 
and  of  wide  experience.  The  latter  had  had  experience  with  'Buf- 
falo gnats'  in  other  localities  (in  the  East)  and  is  well  acquainted 
with  them.  His  close  personal  supervision  of  the  cattle  under  his 
charge,  makes  it  practically  certain  that  he  would  have  discovered 
these  gnats  had  they  been  present  in  the  country." 

"At  the  time  the  study  was  made,  Simtdium  was  breeding  and 
active  in  the  adult  state  in  the  vicinity  of  Dallas,  Texas,  in  the 
eastern  part  of  the  state.  We  have  here  a  region  in  which  cases  of 
pellagra  have  originated,  yet  in  which  Simulium  does  not  and  cannot 
breed." 

Other  possible  insect  vectors  of  pellagra  have  been  studied  in 
great  detail  and  the  available  evidence  indicates  that  if  any  insect 
plays  a  role  in  the  spread  of  the  disease,  Stomoxys  calcitrans  most 
nearly  fills  the  conditions.  This  conclusion  was  announced  by 
Jemiings  and  King  in  191 2,  and  has  been  supported  by  their  subse- 
quent work. 

Yet,  after  all  the  studies  of  the  past  decade,  the  old  belief  that 
pellagra  is  essentially  of  dietarv'  origin  is  gaining  ground.  Gold- 
berger.  Waring  and  Willets  (19 14)  of  the  United  States  Public  Health 


2  52  Arthropod  Transmission  of  Disease 

Service  siimmarize  their  conclusions  in  the  statement,  (i)  that  it  is 
dependent  on  some  yet  undetermined  fault  in  a  diet  in  which  the 
animal  or  leguminous  protein  component  is  disproportionately  large 
and  (2)  that  no  pellagra  develops  in  those  who  consume  a  mixed, 
well-balanced,  and  varied  diet,  such,  for  example,  as  that  furnished 
by  the  Government  to  the  enlisted  men  of  the  Army,  Navy,  and 
Marine  Corps. 

Leprosy 

Leprosy  is  a  specific,  infectious  disease  due  to  Bacillus  leprce,  and 
characterized  by  the  formation  of  tubercular  nodules,  ulcerations, 
and  disturbances  of  sensation.  In  spite  of  the  long  time  that  the 
disease  has  been  known  and  the  dread  with  which  it  is  regarded, 
little  is  known  concerning  the  method  of  transfer  of  the  causative 
organism  or  the  means  by  which  it  gains  access  to  the  human  body. 

It  is  known  that  the  bacilli  are  to  be  found  in  the  tubercles,  the 
scurf  of  the  skin,  nasal  secretions,  the  sputum  and,  in  fact  in  prac- 
tically all  the  discharges  of  the  leper.  Under  such  conditions  it  is 
quite  conceivable  that  they  may  be  transferred  in  some  instances 
from  diseased  to  healthy  individuals  through  the  agency  of  insects 
and  other  arthropods.  Many  attempts  have  been  made  to  demon- 
strate this  method  of  spread  of  the  disease,  but  with  little  success. 

Of  the  suggested  insect  carriers  none  seem  to  meet  the  conditions 
better  than  mosquitoes,  and  there  are  many  suggestions  in  literature 
that  these  insects  play  an  important  r61e  in  the  transmission  of 
leprosy.  The  literature  has  been  reviewed  and  important  experi- 
mental evidence  presented  by  Currie  (19 10).  He  found  that  mosqui- 
toes feeding,  under  natural  conditions,  upon  cases  of  nodular  leprosy 
so  rarely,  if  ever,  imbibe  the  lepra  bacillus  that  they  cannot  be 
regarded  as  one  of  the  ordinary  means  of  transference  of  this  bacillus 
from  lepers  to  the  skin  of  healthy  persons.  He  believes  that  the 
reason  that  mosquitoes  that  have  fed  on  lepers  do  not  contain  the 
lepra  bacillus  is  that  when  these  insects  feed  they  insert  their  probos- 
cis directly  into  a  blood  vessel  and  thus  obtain  bacilli-free  blood, 
unmixed  witl^  lymph. 

The  same  worker  undertook  to  determine  whether  flies  are  able 
to  transmit  leprosy.  He  experimented  with  five  species  found  in 
Honolulu, — Musca  domestica,  Sarcophaga  pallinervis,  Sarcophaga 
barbaia,  Volucella  obesa  and  an  undetermined  species  of  Lucilia. 
The  experiments  with  Musca  domestica  were  the  most   detailed. 


Leprosy  253 

From  these  experiments  he  concluded,  first,  that  all  of  the  above- 
named  flies,  when  j^iven  an  opportunity  to  feed  upon  leprous  fluids, 
will  contain  the  bacilli  in  their  intestinal  tracts  and  feces  for  several 
days  after  such  feeding.  Second,  that  considering  the  habits  of 
these  flies,  and  especially  those  of  Musca  domestica,  it  is  certain  that, 
given  an  exposed  leprous  ulcer,  these  insects  will  frequently  convey 
immense  numbers  of  lepra  bacilli,  directly  or  indirectly,  to  the  skins, 
nasal  mucosa,  and  digestive  tracts  of  healthy  persons.  Additional 
evidence  along  this  line  has  recently  been  brought  forward  by 
Honeij  and  Parker  (19 14),  who  incriminate  both  Musca  domestica 
and  Stomoxys  calcitrans.  Whether  or  not  such  insect -borne  bacilli 
are  capable  of  infecting  persons  whose  skin  and  mucosa  are  thus 
contaminated,  Currie  was  unwilling  to  maintain,  but  he  concludes 
that  until  we  have  more  accurate  knowledge  on  this  point,  we  are 
justified  in  regarding  these  insects  with  grave  suspicion  of  being 
one  of  the  means  of  disseminating  leprous  infection. 

Various  students  of  the  subject  have  suggested  that  bed-bugs 
may  be  the  carriers  of  leprosy  and  have  determined  the  presence  of 
acid-fast  bacilli  in  the  intestines  of  bed-bugs  which  had  fed  on  leprous 
patients.  Opposed  to  this,  the  careful  experiments  of  Thompson 
(19 13)  and  of  vSkelton  and  Parkham  (19 13)  have  been  wholly  nega- 
tive. 

Borrel  has  recently  suggested  that  Demodex,  may  play  a  role  in 
spreading  the  infection  in  families.  Many  other  insects  and  acariens 
have  been  suggested  as  possible  vectors,  but  the  experimental  data 
are  few  and  in  no  wise  conclusive.  The  most  that  can  be  said  is  that 
it  is  quite  possible  that  under  favorable  conditions  the  infection 
might  be  spread  by  any  of  the  several  blood-sucking  forms  or  by 
house-flies. 

Verruga  peruviana 

Verruga  peruviana  is  defined  by  Castellani  and  Chalmers  as  "a 
chronic,  endemic,  specific,  general  disorder  of  unknown  origin,  not 
contagious,  but  apparently  inoculable,  and  characterized  b\'  an  ir- 
regular fever  associated  with  rheumatoid  pains,  anemia,  followed 
by  granulomatous  swellings  in  the  skin,  mucous  membranes,  and 
organs  of  the  body."  It  has  been  generally  believed  by  medical 
men  interested  that  the  comparatively  benign  eruptive  verruga  is 
identical  with  the  so-called  Oroya,  or  Carrion's  fever,  a  malignant 
type.  This  view  is  not  supported  by  the  work  of  Strong,  Tyzzer 
and  Brues,  (1913). 


2  54  Arthropod  Transmission  of  Disease 

The  disease  is  confined  to  South  America  and  to  definitely  Hmited 
areas  of  those  countries  in  which  it  does  occur.  It  is  especially 
prevalent  in  some  parts  of  Peru. 

The  causative  organism  and  the  method  of  transfer  of  verruga 
are  unknown.  Castellani  and  Chalmers  pointed  out  in  1910  that  the 
study  of  the  distribution  of  the  disease  in  Peru  would  impress  one 
with  the  similarity  to  the  distribution  of  the  Rocky  Mountain  fever 
and  would  lead  to  the  conclusion  that  the  aetiological  cause  must  in 
some  way  be  associated  with  some  blood-sucking  animal,  perhaps  an 
arachnid,  and  that  this  is  supported  by  the  fact  that  the  persons 
most  prone  to  the  infection  are  those  who  work  in  the  fields. 

More  recently,  Townsend  (19 13),  in  a  series  of  papers,  has  main- 
tained that  verruga  and  Carrion's  disease  are  identical,  and  that  they 
are  transmitted  to  man  by  the  bites  of  the  Psychodid  fly,  Phlebotomus 
verrucarum.  He  succeeded  in  producing  the  eruptive  type  of  the 
disease  in  experimental  animals  by  injecting  a  physiological  salt 
trituration  of  wild  Phlebotomus  flies.  A  cebus  monkey  was  exposed 
from  October  10  to  November  6,  by  chaining  him  to  a  tree  in  the 
verruga  zone,  next  to  a  stone  wall  from  which  the  flies  emerged  in 
large  numbers  every. night.  Miliar  eruption  began  to  appear  on  the 
orbits  November  13  and  by  November  21,  there  were  a  number  of 
typical  eruptions,  with  exudation  on  various  parts  of  the  body 
exactly  like  miliar  cruptiA^e  sores  commonly  seen  on  legs  of  human 
cases. 

An  assistant  in  the  verruga  work,  George  E.  Nicholson,  contracted 
the  eruptive  type  of  the  disease,  apparently  as  a  result  of  being  bitten 
b}'  the  Phlebotomus  flies.  He  had  slept  in  a  verruga  zone,  under  a 
tight  net.  During  the  night  he  evidently  put  his  hands  in  contact 
with  the  net,  for  in  the  morning  there  were  fifty-five  unmistakable 
Phlebotomus  bites  on  the  backs  of  his  hands  and  wrists. 

Townsend  believes  that  in  nature,  lizards  constitute  the  reservoir 
of  the  disease  and  that  it  is  from  them  that  the  Phlebotomus  flies 
receive  the  infection. 

Cancer 

There  are  not  wanting  suggestions  that  this  dread  disease  is 
carried,  or  even  caused,  by  arthropods.  Borrel  (1909)  stated  that 
he  had  found  mites  of  the  genus  Demodex  in  carcinoma  of  the  face 
and  of  the  mammse.  He  believed  that  they  acted  as  carriers  of  the 
virus. 


Cancer  255 

vSaul  (1910)  and  Dahl  (19 10)  go  much  turther,  since  they  attribute 
the  production  of  the  malignant  growth  to  the  ])resence  of  mites 
which  Saul  had  found  in  cancers.  These  Dahl  described  as  belonging 
to  a  new  species,  which  he  designated  Tarsonemus  hominis.  These 
findings  ha\'c  since  been  confirmed  by  several  workers.  Neverthe- 
less, the  presence  of  the  mite  is  so  rare  that  it  cannot  be  regarded  as 
an  important  factor  in  the  causation  of  the  disease.  The  theory 
that  cancer  is  caused  by  an  external  parasite  is  given  little  credence 
by  investigators  in  this  field. 

In  conclusion,  it  should  be  noted  that  the  medical  and  entomolog- 
ical literature  of  the  past  few  years  abounds  in  suggestions,  and  in 
unsui^ported  direct  statements  that  various  other  diseases  are  insect- 
bonic.  Knab  (191 2)  has  well  said  "vSince  the  discovery  that  certain 
blood-sucking  insects  are  the  secondary  hosts  of  pathogenic  para- 
sites, nearly  every  insect  that  sucks  blood,  whether  habitually  or 
occasionally,  has  been  suspected  or  considered  a  possible  transmitter 
of  disease.  No  thought  seems  to  have  been  given  to  the  conditions 
and  the  characteristics  of  the  individual  species  of  blood-sucking 
insects,  which  make  disease  transmission  possible." 

He  points  out  that ' '  in  order  to  be  a  potential  transmitter  of  human 
blood-parasites,  an  insect  must  be  closely  associated  \vith  man  and 
normalh'  have  opportunity  to  suck  his  blood  repeatedly.  It  is  not 
sufficient  that  occasional  specimens  bite  man,  as,  for  example,  is  the 
case  with  forest  mosquitoes.  Although  a  person  may  be  bitten  by  a 
large  number  of  such  mosquitoes,  the  chances  that  any  of  these 
mosquitoes  survdve  to  develop  the  parasites  in  question,  (assuming 
such  development  to  be  possible),  and  then  find  opportunity  to  bite 
and  infect  another  person,  are  altogether  too  remote.  Applying 
this  criterion,  not  only  the  majority  of  mosquitoes  but  many  other 
blood-sucking  insects,  such  as  Tabanidae  and  Simuliidas,  may  be 
confidently  eliminated.  Moreover,  these  insects  are  mostly  in 
evidence  only  during  a  brief  season,  so  that  we  have  an  additional 
difficult}'  of  a  very  long  interval  during  which  there  could  be  no  prop- 
agation of  the  disease  in  question."  He  makes  an  exception  of 
tick-borne  diseases,  where  the  parasites  are  directly  transmitted  from 
the  tick  host  to  its  offspring  and  where,  for  this  reason,  the  insect 
remains  a  potential  transmitter  for  a  very  long  period.  He  also 
cites  the  trypanosome  diseases  as  possible  exceptions,  since  the  causa- 
tive organisms  apparently  thrive  in  a  number  of  different  \'ertebrate 
hosts  and  mav  be  transmitted  from  cattle,  or  wild  animals,  to  man. 


256  Arthropods  Transmission  of  Disease 

Knab's  article  should  serv^e  a  valuable  end  in  checking  irrespon- 
sible theorizing  on  the  subject  of  insect  transmission  of  disease. 
Nevertheless,  the  principles  which  he  laid  down  cannot  be  applied 
to  the  cases  of  accidental  carriage  of  bacterial  diseases,  or'  to  those 
of  direct  inoculation  of  pyogenic  organisms,  or  of  blood  parasites 
such  as  the  bacillus  of  anthrax,  or  of  bubonic  plague.  Accumulated 
evidence  has  justified  the  conclusion  that  certain  trypanosomes 
pathogenic  to  man  are  harbored  by  wild  mammals,  and  so  form  an 
exception.  Townsend  believes  that  lizards  constitute  the  natural 
reservoir  of  verruga;  and  it  seems  probable  that  field  mice  harbor 
the  organism  of  tsutsugamushi  disease.  Such  instances  are  likely  to 
accumulate  as  our  knowledge  of  the  relation  of  arthropods  to  disease 
broadens. 


;CHAPTER  XII 

HOMINOXIOUS  ARTHROPODS 

The  follo\ving  synoptic  tables  are  presented  in  the  hope  that  they 
niay  be  of  service  in  giving  the  reader  a  perspective  of  the  relation- 
ships of  the  Arthropoda  in  general  and  enabling  him  to  identify  the 
more  important  species  which  have  been  foiind  noxious  to  man. 
Though  applicable  chiefly  to  the  arthropods  found  in  the  United 
States,  exotic  genera  and  species  which  are  concerned  in  the  trans- 
mission of  disease  are  also  included.  For  this  reason  the  keys  to  the 
genera  of  the  Muscids  of  the  world  are  given.  As  will  be  seen,  the 
tables  embrace  a  number  of  groups  of  species  which  are  not  injurious. 
This  was  fotmd  necessary  in  order  that  the  student  might  not  be 
lead  to  an  erroneous  determination  which  would  result  were  he  to 
attempt  to  identify  a  species  which  heretofore  had  not  been  considered 
noxious,  by  means  of  a  key  containing  only  the  noxious  forms.  The 
names  printed  in  bold  faced  type  indicate  the  hominoxious  arthropods 
which  have  been  most  commonly  mentioned  in  literature. 

CRUSTACEA 

Arthropods  having  two  pairs  of  antennae  which  are  sometimes 
modified  for  grasping,  and  usually  with  more  than  five  pairs  of  legs. 
With  but  few  exceptions  they  are  aquatic  creatures.  Representatives 
are:  Crabs,  lobsters,  shrimps,  crayfish,  water-fleas,  and  woodlice. 
To  this  class  belongs  the  Cyclops  (fig.  122)  a  genus  of  minute  aquatic 
crustaceans  of  which  at  least  one  species  harbors  Dracunculus  medi- 
nensis,  the  Guinea  worm  (fig.   121). 

MYRIAPODA 

Elongate,  usually  vermiform,  wnngless,  terrestrial  creatures  having 
one  pair  of  antennae,  legs  attached  to  each  of  the  many  intermediate 
body  segments.  This  group  is  divided  into  two  sections,  now  usually 
given  class  rank:  the  Diplopoda  or  millipeds  (fig.  13),  commonl}^ 
knowTi  as  thousand  legs,  characterized  by  having  two  pairs  of  legs 
attached  to  each  intermediate  body  segment,  and  the  Chilopoda 
or  centipeds  (fig.  14)  having  only  one  pair  of  legs  to  each  body  seg- 
ment. 

257 


2S8 


Hominoxious  Arthropods 
ARACHNIDA 


In  this  class  the  antennae  are  apparently  wanting,  wings  are  never 
present,  and  the  adults  are  usually  provided  with  four  pairs  of  legs. 
Scorpions,  harvest-men,  spiders,  mites,  etc. 

HEXAPODA  (Insects) 

True  insects  have  a  single  pair  of  antennae,  which  is  rarely  vestigial, 
and  usually  one  or  two  pairs  of  wings  in  the  adult  stage.  Familiar 
examples  are  cockroaches,  crickets,  grasshoppers,  bugs,  dragonflies, 
butterflies,  moths,  mosquitoes,  flics,  beetles,  ants,  bees  and  wasps. 

ORDERS   OF  THE  ARACHNIDA 

a.  Abdomen    distinctly    segmented.     A    group    of    orders  including    scorpions, 
(fig.    ii),    whip-scorpions   (fig.    lo),  pseudo-scorpions,    solpugids    (fig.    12) 

harvest-men  (daddy-long-legs  or  harvestmen) ,  etc ArthrogastrA 

aa.  Abdomen    unsegmented,    though    sometimes    with    numerous    annulations 

SPH.a;ROGASTRA 

b.  A  constriction  between  cephalothorax  and  abdomen  (fig.  7).    True  Spiders 

Araneida 

bb.  No  deep  constriction  between  these  parts. 

c.  Legs  usually  well  developed,  body  more  or  less  depressed  (fig.  49).     Mites 

ACARINA 

cc.  Legs  stumpy  or  absent,  body  more  or  less  elongate  or  vermiform,  or  if 
shorter,  the  species  is  aquatic  or  semi-aquatic  in  habit, 
d.  Four  pairs  of  short  legs;    species  inhabiting  moss  or  water.     Water- 
bears  Tardigrada 

dd.  Two  pairs  of  clasping  organs  near  the  mouth,  instead  of  legs,  in  the 

adult;     wonn-like   creatures  parasitic  within  the  nasal  passages, 

lungs,  etc.  of  mammals  and   reptUes    (fig.    148).     Tongue   worms. 

LiNGUATULINA 


148.     Linguatula,  (a)  larva;  (enlarged).       (6)  adult;     (natural  size). 


Acarina  259 

ACARINA* 

a.  Abdomen  annulate,  elongate;    very  minute  forms,  often  with  but  four  legs 
(fig.  62) DEMODICOIDEA 

b.  With  but  four  legs  of  five  segments  each.    Living  on  plants,  often  forming 

galls ERIOPHYIDiE 

bb.  With  eight  legs,  of  three  seginents  each.     Living  in  the  skin  of  mammals 

Demodicid^ 

To  this  family  belongs  the  genus  Demodex  found  in  the  sebaceous  glands 
and  hair  follicles  of  various  mammals,  including  man.     D.  phylloides 
Csokor  has  been  found  in  Canada  on  swine,  causing  white  tubercles 
on  the  skin.     D.  bovis  Stiles  has  been  reported  from  the  United  States 
on  cattle,  upon  the  skin  of  which  they  form  swellings.    D.  folliculorum 
Simon  is  the  species  found  on  man.     See  page  78. 
aa.  Abdomen  not  annulate  nor  prolonged  behind;   eight  legs  in  the  adult  stage, 
b.  With  a  distinct  spiracle  upon  a  stigmal  plate  on  each  side  of  the  body  (usu- 
ally ventral)  above  the  third  or  fourth  coxae  or  a  little  behind  (fig.  50) ; 
palpi  free;    skin  often  coriaceous  or  leathery;   tarsi  often  with  a  sucker. 
c.  Hypostome  large  (fig.  50),  furnished  below  with  many  recurved  teeth; 
venter   with   furrows,    skin   leathery;    large   forms,  usually   parasitic 

IXODOIDEA 

d.  Without  scutum  but  covered  by  a  more  or  less  uniform  leathery  integu- 
ment; festoons  absent;  coxae  unarmed,  tarsi  without  ventral  spurs; 
pul villi  absent  or  vestigial  in  the  adults;    palpi  cylindrical;    sexual 

dimorphism  slight Argasid^ 

e.  Body  flattened,  oval  or  rounded,  with  a  distinct  flattened  margin 
differing  in  structure  from  the  general  integument;  this  margin 
gives  the  body  a  sharp  edge  which  is  not  entirely  obliterated  even 
when  the  tick  is  full  fed.  Capitulum  (in  adults  and  nymphs) 
entirely  invisible  dorsally,  distant  in  the  adult  by  about  its  own 

length  from  the  anterior  border.     Eyes  absent Argus  Latr. 

f.  Body  oblong;   margin  with  quadrangular  cells;   anterior  tibiae  and 
metatarsi  each  about  three  times  as  long  as  broad.     On  poultry, 

southwest  United  States A.  persicus  miniatus 

A.  brevipes  Banks,  a  species  with  proportionately  shorter  legs  has 
been  recorded  from  Arizona, 
ff.  With  another  combination  of  characters.     About  six  other  species 
of  Argas  from  various  parts  of  the  world,  parasitic  on  birds  and 
mammals, 
ee.  Body  flattened  when  unfed,  but  usually  becoming  very  convex  on 
distention;    anterior  end  more  or  less  pointed  and  hoodlike; 
margin  thick  and  not  clearly  defined,  similar  in  structure  to  the 
rest  of  the  integument  and  generally  disappearing  on  distention; 
capitulum  subterminal,  its  anterior  portions  often  visible  dorsally 
in  the  adult;    eyes  present  in  some  species, 
f.  Integument   pitted,    without   rounded   tubercles;     body   provided 
with  many  short  stiff  bristles;    eyes  absent.     On  horses,  cattle 

and  man  (fig.  48) Otiobius  Banks. 

O.megnini,  a  widely  distributed  species,  is  the  type  of  this  genus. 
♦Adapted  from  Banks,  Nuttall,  Warburton,  Stiles,  et,  al. 


26o  Hominoxious  Arthropods 

ii.  Integument  with  rounded  tubercles  or  granules;  body  without  stiff 

bristles Omithodoros  Koch. 

g.  Two  pairs  of  eyes;  tarsi  IV  with  a  prominent  subterminal  spur 
above;     leg    I    strongly    roughened.     On    cattle   and   man. 

O.  coriaceus 

gg.  No  eyes;    no  such  spur  on  the  hind  tarsi. 

h.  Tarsi   I   without  humps  above 0.   talaje. 

hh.  Tarsi  I  with  humps  above. 

i.  Tarsi   IV  without  distinct  humps  above.     On  hogs,  cattle 

and  man O.  turicata 

ii.  Tarsi  IV  with  humps  nearly  equidistant  (fig.  142).     Africa. 
O.  moubata 


a/toom. 


149.      Hasmaphysalis  wellingtoni.      Note  short  palpi,      .^fter  Nuttall  and  Warburton. 


fj-fa-nij 


dd.  With  scutum  or  shield  (fig.  50);  festoons  usually  present;  coxte 
usually  armed  with  spurs,  tarsi  generally  with  one  or  two  ventral 
spurs;  pulvilli  present  in  the  adults;   sexual  dimorphism  pronounced 

IXODIDiE 

e.  With  anal  grooves  surrounding  anus  in  front ;  inornate;  without  eyes; 
no  posterior  marginal  festoons;  venter  of  the  male  with  non- 
salient  plates.  Numerous  species,  14  from  the  United  States, 
among  them  I.  ricinus  (fig.  49  and  50),  scapularis,  cookei,  laexa- 
gonus,  bicornis.  Ixodes  Latr.     (including    Ceratixodes). 

ee.  With  anal  groove  contouring  anus  behind,  or  groove  faint  or  obsolete, 
f.  With  short  palpi  (fig.  149). 

g.  Without  eyes,  inornate,  with  posterior  marginal   festoons;   male 
without    ventral    plates.     Numerous    species.     H.    chordeilis 

and  leporis-palustris  from  the  United  States 

Ilcemaphysalis  Koch. 


Acarina 


261 


150.  Stigmal  plate  of  Dermacentor  andersoni;  (a)  of  male,  (6)  of  female.  After  Stiles, 
(c)  permacentor  variabilis,  male-  (d)  Glyciphagus  obesus;  («)  Otodectes 
cynotis;  (/)  Tyroglyphus  lintneri;  (g)  Tarsonemus  pallidus;  (h)  anal  plate 
and  mand'ble  of  Liponyssus;    (e)  to  {h)  after  Bank?. 


262 


Hominoxious  Arthropods 


gg.  With  eyes. 

h.  Anal  groove  distinct;    posterior  marginal  festoons  present. 
i.  Base   of   the   capitulum    (fig.    150c)    rectangular   dorsally; 

usually  ornate Dermacentor  Koch. 

j.  Adults  with  four  longitudinal  rows  of  large  denticles  on 
each  half  of  hypostome;  stigmal  plate  nearly  circular, 
without  dorso-lateral  prolongation,  goblets  very  large, 
attaining  43/*  to  115M  in  diameter;  not  over  40  per 
plate,  each  plate  surrounded  by  an  elevated  row  of 
regularly  arranged  supporting  cells;  white  rust  want- 
ing; base  of  capitulum  distinctly  broader  than  long, 
its  postero-lateral  angles  prolonged  slightly,  if  at  all; 
coxae  I  with  short  spurs;  trochanter  I  with  small 
dorso-terminal  blade.     Texas,  Arizona,  etc.     D.  nitens 


araofe 


Jc 


151.     Rhipicephalus  bursa,  male. 
After  Nuttall  and  Warburton. 


jj.  Adults  with  three  longitudinal  rows  of  large  denticles  on 
each   half  of  hypostome;     goblet   cells  always  more 
than  40  per  plate;   whitish  rust  usually  present, 
k.  Dorso-lateral  prolongation  of  stigmal  plate  small  or 
absent;    plates  of  the  adults  distinctly  longer  than 
broad;    goblet   cells   large,    usually  30M   to   85M  in 
diameter,  appearing  as  very  coarse  punctations  on 
untreated    specimens,    but    on    specimens    treated 
with  caustic  potash  they  appear  very  distinct  in 
outline;   base  of  capitulum  distinctly  (usually  about 
twice)  broader  than  long,  the  postero-lateral  angles 
distinctly  produced  caudad;    spurs  of  coxae  I  long, 
lateral    spur    slightly    longer    than    median;     tro- 
chanter I  with  dorso-terminal  spur.     D.  albipicHis, 
(=  variegatus),  salmoni,  nigrolineatus. 


Acarina  .  263 

kk.  Dorso-lateral  prolongation  of  stigmal  plate  distinct. 
1.  Body  of  plate  distinctly  longer  than  broad;    goblet 
cells  of  medium  size,  usually  17.5M  to  35^  or  40/a  in 
diameter,    appearing    as   medium   sized    punctua- 
tions on  untreated  specimens,  but  on  the  speci- 
mens  treated    with    caustic    potash    they   appear 
very    distinct   in   outline,    which   is   not   circular; 
base  of  capitulum  usually  less  than  twice  as  broad 
as    long,    the    postero-lateral    angles    always    dis- 
tinctly prolonged  caudad. 
m.  Trochanter    I    with    distinct    dorso-subterminal 
retrograde     sharp,     digitate     spur;      postero- 
lateral    angles     of     capitulum     pronouncedly 
prolonged   caudal,   ii2ai   to    160^  long;  goblet 
cells    attain     13^1  to    40^1    in   diameter;   type 

locality   California D.  occidentalis 

mm.  Trochanter  I  with  dorso-terminal  blade ;  postero- 
lateral angles  of  capitulum  with  rather  short 
prolongations, 
n.  Stigmal  plate  small,  goblet  cells  not  exceeding 
45  in  the  male  or  100  in  the  female;  scutum 
with  little  rust,  coxa  I  with  short  spurs,  the 
inner     distinctly     shorter     than     the     outer 

D.    parumapertus-marginatus 

nn.  Stigmal  plate  larger;  goblet  cells  over  70  in 
the  male  and  over  100  in  the  female;  coxa  I 
with  longer  spurs,  inner  slightly  shorter 
than  the  outer;    scutum  with  considerable 

rust D.  venustus* 

11.  Goblet  cells  small,  rarely  exceeding  1 7. 6/a,  occasional- 
ly reaching  19/^  in  diameter;  on  untreated  speci- 
mens they  appear  as  very  fine  granulations,  and  on 
specimens  treated  with  caustic  potash  they  may 
be  difficult  to  see,  but  their  large  number  can 
be  determined  from  the  prominent  stems  of  the 
goblets;  surface  of  outline  of  the  goblets  dis- 
tinctly circular;  base  of  the  capitulum  usually  less 
than  twice  as  broad  as  long,  the  postero-lateral 
angle     distinctly    prolonged     caudad;  spurs     of 

coxae  I  long 

D.    reticulatus   and  electus    (  =  variabilis?) 

ii.  Base  of  the  capitulum  (fig.  151)  usually  hexagonal  (except 
in  the  male  of  puchellns) ;  and  usually  inornate. 


*Dr.  C.  W.  Stiles  considers  the  species  which  is  responsible  for  spotted  fever  distinct  from  the 
venustus  of  Banks,  separating  it  as  follows: 

Goblet  cells  about  75  in  the  male  or  10s  in  the  female.     Texas.     D.  venustus. 

Goblet  cells  157  in  the  male,  or  120  in  the  female;  stigmal  plate  shaped  as  shown  in  the  figure 
(figs.  i,>;o  a,  b).     Montana,  etc.     D.  andersoni. 


264 


Hominoxtous  Arthropods 


]• 


ih 


No  ventral  plate  or  shield  in  either  sex  (fig.  153).  R. 
bicomis  from  the  United  States  ....  Rhipicentor  Nuttall 
Males  with  a  pair  of  adanal  shields,  and  usuaU}^  a  pair  of 
accessor^'  adanal  shields.  Nvunerous  species,  among 
them  R.  sanguineus  (fig.  154)  and  texanus,  the  latter 

from    the    United    States Rhipicephalus    Koch 

hh.  Anal  grooves  faint  or  obsolete;  no  marginal  festoons. 

i.  Short  palpi;  highly  chitinized;  unfed  adults  of  large  size; 
coxa;  conical;  male  with  a  median  plate  prolonged  in  two 
long  spines  projecting  caudad;    segments  of  leg  pair  IV 

greatly  swollen  (fig.  155,  156).     M.  winthemi 

Margaropus    Karsch 


152. 


Monieziella  (Histiogaster)  emtomophaga-spermatica,  ventral  aspect, 
male  and  female.     After  Trouessart, 


ii.  Very  short  palpi,  ridged  dorsally  and  laterally;  slightly 
chitinized;  unfed  adults  of  smaller  size;  coxae  I  bifid; 
male  with  adanal  and  accessor}'  adanal  shields  (fig.  139). 

B,  annulatus Boophilus  Curtis 

ff.  Palpi  longer  than  broad  (fig.  157). 

g.  Male  with  pair  of  adanal  shields,  and  two  posterior  abdominal 
protrusions  capped  by  chitinized  points;  festoons  present  or 
absent.     Several  species,  among  them  H.  aegypticum  (fig.  140) 

from    the    old    world Hyalomma  Koch 

gg.  Male  without  adanal   shields  but   small  ventral  plaques  are 

occassionally  present  close  to  the  festoons.     Many  species,  a 

few  from  the  Unted  States  (fig.  157) ...  .  Amblyomma  Koch 

h.  Coxa  I  with  but  one  spine;    metatarsi   (except  I)  with  two 

thickened    spurs    at    tips A.    maculatum 

lih.  Coxa  I  with  two  spines;    metatarsi  without  stout  spurs  at 
tips,  only  slender  hairs. 


Acarina 


265 


Projections  of  coxa  I  blunt  and  short.     Large  species  on  the 

gopher    tortoise    in    Florida A.    tuberculatum 

.  Projections  of  coxa  I  longer,  and  at  least  one  of  them  sharp 

pointed;    second  segment  of  palpus  twice  as  long  as  the 

third;   coxa  IV  of  the  male  with  a  long  spine. 

j.  Porose  areas  nearly  circular;    shield  of  both  sexes  pale 

yellowish,  with  some  silvery  streaks  and  marks,  and 

some  reddish  spots;    shield  of  female  as  broad  as  long. 

A.  cajennense  (  =mixtuni). 

jj.  Porose  areas  elongate,  shield  brown,  in  the  female  with 
an  apical  silvery  mark,  in  the  male  with  two  small 
and  two  or  four  other  silvery  spots;  shield  of  the  fe- 
male longer  than  broad  (fig   158  e).  .A.  americanum. 


J'nicrna.l   spur 
ExttrnoiL  spK-n 


^Ic^nU^tltX 


Sp/rac/e— 


■JCS^OO  t)^ 


153.     Rhipicentor  bicornis,  ventral  aspect,  male.     After  Nuttall  and 
Warburton. 

Hypostome  small,  without  teeth,  venter  without  furrows;    body  often 
with  coriaceous  shields,  posterior  margin  of  the  body  never  crenulate 

(i.e.     without    festoons);      no    eyes GAMASOIDEA. 

I.  Parasitic  on  vertebrates ;  mandibles  fitted  for  piercing;  body  sometimes 

constricted     Dermanyssid^. 

e.  Anal    plate    present Dermanyssin^e. 

f.  Body  short;   legs  stout,  hind  pair  reaching  much  beyond  the  tip  of 

the  body.     On  bats Pteroptus  Dufour. 

ff.  Body  long;  hind  legs  not  reaching  beyond  the  tip  of  the  body, 
g.  Peritreme  on   the   dorsum,   verj^  short;    body  distinctly  con- 
stricted   Ptilonyssus  Berl. 

gg.  Peritreme  on  the  venter,   longer;    body  not  distinctly  con- 
stricted, 
h.  Mandibles  in  both  sexes  chelate.     Parasitic  on  bats,  mice 

and  birds  (fig.  150,  h) Liponyssus  Kol. 

The  species  L.  (=Leiognathus)  sylviarum  frequents  the 
nests  of  warblers.  An  instance  is  on  record  of  these  mites 
attacking  man,  causing  a  pruritis. 


266 


Hominoxious  Arthropods 


hh.  Mandibles  in  the  male  chelate  (fig.  158  j),  in  the  female  long, 

styliform.     Parasitic   on   birds Dermanyssus    Dug, 

Two  species  of  importance  ma}^  be  noted,  D.  hirundinus 
and  D.   gallinae.     The  latter    (fig.   51)  is  a  serious  pest 
of   poultry,    sometimes   attacking    man,    causing   itching 
and  soreness, 
ee.  Anal  plate  absent.     In  lungs  and  air  passages  of  some  mammals. 

Halarachnin^. 

dd.  Free  or  attached  to  insects,  rarely  on  vertebrates. 

e.  First  pair  of  legs  inserted  within  the  same  body  opening  as  the  oral 
tube;  genital  apertures  surrounded  by  the  sternum.  On  in- 
sects   TjROPODIDiE. 


(fic/ii^fuil.  spun. 


9- 


1.34.  Rhicephalus  sanguineus,  male. 
After  Nuttall  and  Warbur- 
ton. 


ee.  First  pair  of  legs  inserted  at  one  side  of  the  mouth  opening;   male 
genital  aperture  usually    on    the  anterior  margin  of  the  sternal 

plate    Gamasidae. 

This  family  contains  a  number  of  genera,  some  of  which  are  found 
upon  mammals,  though  the  majority  affect  only  other  artho- 
pods.  One  species,  Laelaps  stabularis,  frequents  the  bedding 
in  stables,  and  in  one  instance  at  least,  has  occasioned  irri- 
tation and  itching,  in  man. 
bb.  N.o  distinct  spiracle  in  the  stigmal  plate  on  each  side  of  the  body. 

c.  Body  usually  coriaceous,  with  few  hairs,  with  a  specialized  seta  arising 
from  a  pore  near  each  posterior  corner  of  the  cephalothorax ;  no  eyes; 
mouth  parts  and  palpi  very  small;    ventral  openings  of  the  abdomen 

large;  tarsi  without  sucker.    Not  parasitic ORIBATOIDEA. 

cc.  Body  softer;    without  such  specialized  seta. 

d.  Aquatic  species HYDRACHNOIDEA 

dd.  Not  aquatic. 


Acarina 


267 


Palpi  small,  three  segmented,  adhering  for  some  distance  to  the  lip; 
ventral  suckers  at  genital  opening  or  near  anal  opening  usually 
present;  no  eyes;  tarsi  often  end  in  suckers;  beneath  the  skin  on 
the  venter  are  seen  rod-like  epimcra  that  support  the  legs;    body 

often  entire.     Adults  frequently  parasitic SARCOPTOIDEA. 

f.  With  trachea?;  no  ventral  suckers;  legs  ending  in  claws;  body 
divided  into  cephalothorax  and  abdomen;  the  female  with  a 
clavate    hair    between    legs  I  and  II.     Usually    not    parasitic 

on  birds  and  mammals TarsonemiDjE 

g.  Hind  legs  of  female  ending  in  claw  and  sucker  as  in  the  other 

pairs PEDICULOIDINiE 

To  this  sub-family  belongs  the  genus  Pediculoides 
P.  ventricosus  is  described  on  page  69. 


155.    Margaropus  winthemi,  male.    After 
Nuttall  and  Warburton. 


Margaropus  winthemi. 
capitulum  and  scutum. 
After  Nuttall  and  War- 
burton. 


gg.  Hind  legs  of  the  female  end  in  long  hairs Tarsonemin.*; 

Tarsonemus  intectus  Karpelles,  normally  found  upon  grain, 
is  said  to  attack  man  in   Hungar\'  and   Russia.     Other 
species  of  the  genus  affect  various  plants  (c.f.  fig.  150,  g). 
ff.  Without  tracheae;    no  such  clavate  hair. 

g.     Genital  suckers  usually  present;    integument  usually  without 
fine  parallel  lines, 
h.  Legs  short,   without     clavate  hair  on   tarsi   I   and   II.     On 

insects Canestrinid^. 

hh.  Legs  longer,  with  a  clavate  hair  on  tarsi  I  and  II,     Not 

normally  parasitic  except  on  bees TYROGLYPHID.S 

i    Dorsal  integument  more  or  less  granulate;  claws  ver>^  weak, 
almost  invisible;  some  hairs  of  the  bod}^  plainly  feathered; 

ventral  apertures  large Glyciphagus  Her. 

This  genus  occurs  in  the  United  States.  In  Europe  the 
mites  have  been  found  feeding  on  all  sorts  of  substances. 
They  are  known  as  sugar  mites  and  cause  the  disease 


268  Hominoxious  Arthropods 


known  as  grocer's  itch.     G.  domesticus  and  G.  pru- 
norum  are  old  world  species  (fig.  150,  d). 
.  Dorsal    integtiment    not    grantdate;     claws    distinct;     no 

prominent  feathered  hairs;    ventral  aperture  small, 
j.  Mandibles   not   chelate;     elongate,   and   toothed   below; 
body  without  long  hairs;    palpi  enlarged  at  tip  and 
provided  with  two  divergent  bristles.     Species  feed  on 

decaying    substances Histiostoma    Kram. 

jj.  Mandibles  chelate;    palpi  not  enlarged  at  the  tip,  nor 
with  two  bristles, 
k.  No  clavate  hair  on   the   base  of  tarsi   I  and  II;    no 
suture  between  cephalothorax  and  abdomen.     Live 

on  bees  or  in  their  nests Trichotarsus  Can. 

kk.  A  clavate  or  thickened  hair  at  the  base  of  tarsi  I  and  11. 

I.  The  bristle  on  the  penultimate  segment  of  the  legs 

arises  from  near  the  middle;  no  suture  between  the 
cephalothorax  and  abdomen.  The  species,  some 
of  which  occur  in  the  United  States,  feed  on  dried 
fruit,  etc Carpoglyphus  Robin. 

II.  The  bristle  on  the  penultimate  segment  of  the  legs 

arise  from  near  the  tip ;   a  suture  between  cephalo- 
thorax and  abdomen, 
m.  Cephalothorax  with  four  distinct  and  long  bristles 
in  a  transverse  row;   tarsi  I  and  II  about  twice 
as  long  as  the  preceding  segment   (fig.   150  f) 

Tyroglyphus   Latr. 

n.  Some  bristles  on  tarsi  I  and  II  near  middle, 
distinctly  spine-like;    the  sense  hair  about  its 
length  from  the  base  of  the  segment.     Several 
species  in  the  United  States  belong  to  this 
group, 
nn.  No  spine-like  bristles  near  the  middle  of  the 
tarsi ;   sense  hair  not  its  length  from  the  base 
of  the  segment, 
o.  Of  the  terminal  abdominal  bristles,  only  two 
are  about  as  long  as  the  abdomen ;    1  eg  I 
of  the  male  greatly  thickened  and  with  a 
spine  at  apex  of  the  femur  below .  .  T.  farinse. 
00.  Of  the  terminal  abdominal  bristles  at  least 
six  or  more  are  very  long,  nearly  as  long 
as  the  body, 
p.  Bristles  of  the  body  distinctly  plumose  or 
pectinate ;    tarsi  very  long .  .  T.  longior. 
pp.  Bristles  of  the  body  not  pectinate. 

q.  In  mills,  stored  foods,  grains,  etc.  Third 
and  fourth  joints  of  hind  legs  scarcely 
twice  as  long  as  broad;  abdominal 
bristles    not    unusually    long;     legs    I 


Acarina  269 

and    II    of    the    male    not    unusually 

stout T.  americanus. 

qq.  With     other     characters     and     habits. 
T.   lint  fieri   (fig.    150  f)   the  mushroom 
mite,  and  several  other  species, 
mm.  Cephalothorax    with    but    two    long    distinct 
bristles  (besides  the  frontal  pair),  but  some- 
times   a    very     minute    intermediate    pair; 
tarsi  I  and  II  unusually  short  and  not  twice 
as  long  as  the  preceding  segment, 
n.  Tarsi  with  some  stout  spines .  Rhizoglyphus  Clap. 
The  species  of  this  genus  are  vegetable  feed- 
ers.    Several    occur   in    the    United    States. 
R.  parsiticus  and  R.  spinitarsus  have  been 
recorded  from  the  old  world,  attacking  human 
beings  who  handle  affected  plants, 
nn.  Tarsi  with  only  fine  hairs.  .Monieziella  Berl. 
The  species  of  this  genus,  as  far  as  known, 
are  predaceous  or  feed  on  recently  killed 
animal     matter.     Several     species    occur 
in  the  United  States.     M.  ( =Histiogaster) 
entomophaga     (fig.     152)    from    the    old 
world    has    been    recorded    as    injurious 
to  man. 
gg.  Genital  suckers  absent;    integument  with  fine  parallel  lines. 
Parasitic  on  birds  and  mammals, 
h.  Possessing  a   specially   developed   apparatus   for  clinging   to 

hairs    of    mammals Listrophorid.e. 

hb.  Without  such  apparatus. 

i.  Living    on    the    plumage    of    birds Analgesid.«. 

ii.  In  the  living  tissues  of  birds  and  mammals. 

j.  Vulva  longitudinal.     In  the  skin  and  cellular  tissues  of 

birds CVTOLEICHID.E. 

This  family  contains  two  species,  both  occurring  in  the 
United  States  on  the  common  fowl.  Laminosioptes 
cysticola  occurs  on  the  skin  and  also  bores  into  the 
subcutaneous  tissue  where  it  gives  rise  to  a  cal- 
careous cyst.  Cytoleichus  nudus  is  most  commonly 
found  in  the  air  passages  and  air  cells, 
jj.  Vulva  transverse.     In   the  skin  of  mainmals  and  birds 

SARCOPTIDiE 

k.  Anal  opening  on  the  dorsum. 

I.  Third  pair  of  legs  in  the  male  without  apical  suckers. 

On  cats  and  rabbits Notoedres  Rail. 

The  itch  mite  of  the  cat,  N.  cati  (fig.  61)  has  been 
recorded  on  man. 

II.  Third  leg  in  the  male  with  suckers.     On  bats.  .  .  . 

Prosopodectes    Can. 


270 


Hominoxious  Arthropods 


kk.  Anal  opening  below. 

I.  Pedicel  of  the  suckers  jointed;    mandibles  styliform 

and  serrate  near  the  tip Psoroptes  Ger^^ 

P.  communis  ovis  is  the  cause  of  sheep  scab. 

II.  Pedicel    of    the    suckers    not    jointed;     mandibles 
chelate. 

m.  No  suckers  on  the  legs  of  the  females;    parasitic 

on    birds,    including    chickens.      C.  mulans   is 

itch  mite  of  chickens.      Cnemidocoptes    Fiirst. 

mm.  Suckers  at  least  on  legs  I  and  II;   parasitic  on 

mammals. 

n.  Legs  very  short;    in    the  male  the  hind  pairs 

equal  in  size ;    body  usually  short 

Sarcoptes  Latr. 

S.  scabiei  is  the  itch  mite  of  man  (fig.  56). 


fjj^Uiu        iutitij 


Amblyomma,  female, 
and  Warburton. 


After  Nuttall 


nn.  Legs  more  slender;   in  the  male  the  third  pair 

is  much  larger  than  the  fourth;    body  more 

elongate. 

o.  Female  with  suckers  on   the  fourth  pair  of 

legs.     Species  do  not  burrow  in  the  skin, 

but  produce  a  scab  similar  to  sheep  scab. 

They  occur  in  the  ox,  horse,  sheep  and  goat 

Chorioptes  Gerv. 

C.    symbiotes   bovis   of   the   ox   has   been 
recorded  a  few  times  on  man. 
00.  Female  without  suckers  to  the  fourth  legs, 
p.  Hind  part  of  the  male  abdomen  with  two 

lobes.     On  a  few  wild  animals 

Caparinia   Can. 


Acarina  271 

pp.  Hind  part  of  the  male  abdomen  without 
lobes.     Live  in  ears  of  dogs  and  cats 

Olodecles    Canestr. 

0.  cynotis  Hering  (fig.  150  e)  has  been 

taken  in  the  United  States. 

;.  Palpi  usually  of  four  or  five  segments,  free;    rarely  with  ventral 

suckers  near  genital  or  anal  openings;    eyes  often  present;    tarsi 

never  end  in  suckers;    body  usually  divided  into  cephalo thorax 

and  abdomen;     rod-like   epimera   rarely   visible;    adults   rarely 

parasitic. 

f.  Last  segment  of  the  palpi  never  forms  a  thumb  to  the  preceding 

segment;    palpi  simple,  or  rarely  formed  to  hold  prey;    body 

with   but   few   hairs EUPODOIDEA. 

g.  Palpi  often  geniculate,  or  else  fitted  for  grasping  prey;  mandi- 
bles large  and  snout  like;  cephalothorax  with  four  long 
bristles  above,  two  in  front,  two  behind;  last  segment  of  leg  I 

longer  than  the  preceding  segment,  often  twice  as  long 

Bdellid^. 

gg.  Palpi  never  geniculate  (fig.  158a),  nor  fitted  for  grasping  prey: 
beak  small;  cephalothorax  with  bristles  in  different  arrange- 
ment; last  segment  of  leg  I  shorter  or  but  little  longer  than 
the    preceding    joint;     eyes    when    present    near    posterior 

border    EuPODlD.ffi; 

Moniez  has  described  a  species  from  Belgium  (Tydeus 
molestus)  which  attacks  man.  It  is  rose  colored;  eye- 
less; its  legs  are  scarcely  as  long  as  its  body,  the  hind 
femur  is  not  thickened;  the  mandibles  are  small  and  the 
anal  opening  is  on  the  venter.  The  female  attains  a 
length  of  about  0.3  mm. 
ff .  Last  segment  of  the  palpus  forms  a  thumb  to  the  preceding,  which 
ends  in  a  claw  (with  few   exceptions) ;    body  often  with  mam^ 

hairs    (fig.    158    k) .TROMBIDOIDEA. 

g.  Legs  I  and  II  with  processes  bearing  spines;    skin  with  several 

shields;   coxae  contiguous Cmcvi^idje. 

gg.  Legs  I  and  II  without  such  processes;   few  if  any  shields. 

h.  Palpi  much  thickened  on  the  base,  moving  laterally,  last 

joint  often  with  two  pectinate  bristles;    no  eyes;    legs  I 

ending   in   several   long  hairs;    adult   sometimes   parasitic 

CHEYLETIDiE 

Cheyletus  eruditus,  which  frequents  old  books,  has  once 
been  found  in  pus  discharged  from  the  ear  of  man. 
hh.  Palpi  less  thickened,  moving  vertically;  eyes  usually  present; 
leg  I  not  ending  in  long  hairs, 
i.  Cox£e  contiguous,  radiate;    legs  slender,  bristly;    body  with 

few  hairs;  no  dorsal  groove;   tarsi  not  swollen 

Erythr^id^. 

ii.  Coxa;  more  or  less  in  two  groups;  legs  less  bristly. 


272 


Hontinoxious  Arthropods 


(a)  Tydeus,  beak  and  leg  from  below;  (6)  Cheyletus  pyriformis,  beak  and  palpus; 
(c)  beak  and  claw  of  Pediculoides;  (d)  leg  of  Sarcoptes;  (e)  scutum  of 
female  of  Amblyomma  americana;  (/)  leg  i  and  tip  of  mandible  of  Histio- 
stoma  americana;  (g)  Histiogaster  malus,  mandible  and  venter;  (h)  Aleuro- 
bius  farinae.  and  leg  i  of  male;  (t)  Otodectes  cynotis,  tip  of  abdomen  of  male, 
ij)  beak  and  anal  plate  of  Dermanyssus  gallinae;  {k)  palpus  of  AUothrom- 
bium.     (a)  to  ij)  after  Banks. 


A  carina  273 

j.  Body  with  fewer,  longer  hairs;    often  spinning  threads; 
no    dorsal    groove;     tarsi    never    swollen;     mandibles 

styliform  (for  piercing) Tetranychid^ 

The  genus  Tetranychus  may  be  distinguished  from  the 

other  genera  occurring  in  the  United  States  by  the 

following  characters:     No  scale-like  projections  on 

the  front  of  the  cephalothorax ;    legs  I  as  long  or 

longer  than  the  body ;  palp  ends  in  a  distinct  thumb ; 

the  body  is  about  1.5  times  as  long  as  broad.     T. 

molestissimus  Weyenb.   from   South  America,   and 

T.    telarius    from    Europe    and    America    ordinarily 

infesting  plants,  are  said  also  to  molest  man. 

jj.  Body  with  many  fine  hairs  or  short  spines;   not  spinning 

threads;      often     with     dorsal     groove;     tarsi    often 

swollen. 

k.  Mandibles  styliform  for  piercing.  .  .  .Rhvcholophid.«. 

kk.  Mandibles  chelate,  for  biting TROMBIDIDiE 

The   genus   Trombidium   has   recently   been    sub- 

_. divided   by    Berlese   into   a   number   of   smaller 

ones,  of  which  some  five  or  six  occur  in  the 
United  States.  The  mature  mite  is  not  para- 
sitic but  the  lan.-ae  which  are  ver>-  numerous  in 
certain  localities  will  cause  intense  itching, 
soreness,  and  even  more  serious  complications. 
They  burrow  beneath  the  skin  and  produce 
inflammed  spots.  They  have  received  the 
popular  name  of  "red  bug,"  The  names  Leptus 
americanus  and  L.  irritans  have  been  applied  to 
them,  although  they  are  now  known  to  be  im- 
mature stages.     (Fig.  44.) 

HEXAPODA  (Insecta) 

The  Thysanura  (springtails  and  bn'stletails),  the  Neuropteroids 
(may-flies,  stone-flies,  dragon-flies,  caddis-flies,  etc.),  Mallophaga 
(bird  lice),  Physopoda  (thrips),  Orthoptera  (grasshoppers,  crickets, 
roaches),  are  of  no  special  interest  from  our  viewpoint.  The  remain- 
ing orders  are  briefly  characterized  below. 

SIPHUNCULATA   (page  275) 

Mouth  parts  suctorial;  beak  fleshy,  not  jointed;  insect  wingless; 
parasitic  upon  mammals.     Metamorphosis  incomplete.     Lice. 

HEMIPTERA   (page  275) 

Mouth  parts  suctorial;  beak  or  the  sheath  of  the  beak  jointed; 
in  the  matirre  state  usually  with  four  wings.     In  external  appearance 


274  Hominoxious  Arthropods 

the  immature  insect  resembles  the  adiilt  except  that  the  immature 
form  (i.  e.  nymph)  never  has  wings,  the  successive  instars  during 
the  process  of  growth,  therefore,  are  quite  similar;  and  the  meta- 
morphosis is  thus  incomplete.  To  this  order  belong  the  true  bugs, 
the  plant  lice,  leaf  hoppers,  frog  hoppers,  cicadas,  etc. 

LEPIDOPTERA 

The  adult  insect  has  the  body  covered  with  scales  and  (with  the 
rare  exception  of  the  females  of  a  few  species)  with  four  wings  also 
covered  with  scales.  Proboscis,  when  present,  coiled,  not  seg- 
mented, adapted  for  sucking.  Metamorphosis  complete,  i.e.  the 
young  which  hatches  from  the  egg  is  quite  unlike  the  adult,  and  after 
undergoing  several  molts  transforms  into  a  quiescent  pupa  which  is 
frequently  enclosed  in  a  cocoon  from  which  the  adult  later  emerges. 
The  larvae  are  known  as  caterpillars.     Butterflies  and  moths. 

DIPTERA  (page  285) 

The  adult  insect  is  provided  with  two,  usually  transparent, 
wings,  the  second  pair  of  wings  of  other  insects  being  replaced  by  a 
pair  of  halteres  or  balancers.  In  a  few  rare  species  the  wings,  or 
halteres,  or  both,  are  wanting.  The  mouth  parts,  which  are  not 
segmented,  are  adapted  for  sucking.  The  tarsi  are  five-segmented. 
Metamorphosis  complete.  The  larvae,  which  are  never  provided 
with  jointed  legs,  are  variously  known  as  maggots,  or  grubs,  or 
wrigglers.     Flies,  midges,  mosquitoes. 

SIPHONAPTERA  (page  316) 

Mouth  parts  adapted  for  sucking;  body  naked  or  with  bristles 
and  spines;  prothorax  well  developed;  body  compressed;  tarsi 
with  five  segments;  wings  absent.  Metamorphosis  complete. 
The  larva  is  a  wormlike  creature.     Fleas. 

COLEOPTERA 

Adult  with  four  wings  (rarely  wanting),  the  first  pair  homy  or 
leathery,  veinless,  forming  wing  covers  which  meet  in  a  line  along 
the  middle  of  the  back.  Mouth  parts  of  both  immature  stages  and 
adults  adapted  for  biting  and  chewing.  Metamorphosis  complete. 
The  larvae  of  many  species  are  known  as  grubs.     Beetles. 


Siphunculata  mid  Hemiptera  275 

HYMENOPTERA 

Adult  insect  with  four,  usually  transparent,  wings,  wanting  in 
some  species.  Mouth  parts  adapted  for  biting  and  sucking;  palpi 
small;  tarsi  four  or  five-segmented.  Metamorphosis  complete. 
Parasitic  four-winged  flies,  ants,  bees,  and  wasps. 

SIPHUNCULATA  AND  HEMIPTERA 

a.  Legs  with  claws  fitted  for  clinging  to  hairs;  wings  wanting;  spiracles  of  the 

abdomen   on   the   dorsal    surface.     (  =  ANOPLURA  =  PARASITICA) 

SIPHUNCULATA. 

b.  Legs  not  modified  into  clinging  hooks;    tibia  and  tarsus  ver}^  long  and 
slender;    tibia  without  thumb-like  process;    antennae  five-segmented 

H^MATOMYZID.'E  Endr. 

Hcematomyzus  elephantis  on  the  elephant, 
bb.  Legs  modified  into  clinging  hooks;    tibia  and  tarsus  usually  short  and 
stout;    tibia  with  a  thumb-like  process;    head  not  anteriorly  pro- 
longed, tube-like. 
c.  Body  depressed;   a  pair  of  stigmata  on  the  mesothorax,  and  abdominal 
segments  three  to  eight;    antennae  three  to  five-segmented, 
d.  Eyes  large,  projecting,  distinctly  pigmented;    pharynx  short  and 
broad;    fulturae  (inner  skeleton  of  head)  ver>'  strong  and  broad, 
with  broad  arms;    proboscis  short,  scarcely  attaining  the  thorax. 

Pediculid^ 

e.  Antenna;   three-segmented.     A   few   species   occurring    upon   old 

world  monkeys Pedicinis  Gerv. 

ee.  Antennae  five  -segmented. 

f.  All  legs  stout;  thumb-like  process  of  the  tibia  very  long  and 
slender,  beset  with  strong  spines,  fore  legs  stouter  than  the 
others;  abdomen  elongate,  segments  without  lateral  pro- 
cesses;   the  divided  telson  with  a  conical  process  posteriorly 

upon   the   ventral   side Pediculus    L. 

g.  Upon  man, 

h.  Each  abdominal  segment  dorsally  with  from  one  to  three 
more  or  less  regular  transverse  rows  of  small  setae; 
antenna  about  as  long  as  the  width  of  the  head.     Head 

louse  (fig.  65) P.  humanus. 

hh.  "No  transverse  rows  of  abdominal  setae;    antenna  longer 
than  the  width  of  the  head;    species  larger."     Piaget. 

Body    louse    of    man P.    corporis. 

gg.  Upon   apes   and   other   mammals P.    pusitalus    (?). 

ff.  Fore  legs  delicate,  with  very  long  and  slender  claws;  other  legs 
very  stout  with  short  and  stout  claws;  thumb-like  process  of 
the  tibia  short  and  stout;  abdomen  ver>'  short  and  broad; 
segment  one  to  five  closely  crowded,  thus  the  stigmata  of  seg- 
ments three  to  five  apparently  lying  in  one  segment;  segments 
five   to   eight   with   lateral   processes;     telson   without   lateral 

conical  appendages  (fig.  69).     Crab  louse  of  man 

Phthirus  pubis. 


276 


Hominoxious  Arthropods 


dd.  Eyes  indistinct  or  wanting;    pharyftx  long  and  slender,  fulturae  very- 
slender  and  closely  applied  to  the  pharynx;  proboscis  very  long. 

Several  genera  found  upon  various  mammals HiEMATOPiNiD^E. 

CO.  Body  swollen;  meso-  and  metathorax,  and  abdominal  segments  two  to 
eight  each  with  a  pair  of  stigmata;  eyes  wanting;  antennae  four  or 
five-segmented ;   body  covered  with  stout  spines.     Three  genera  found 

upon     marine     mammals Echinophthiriid.e 

a.  Legs  fitted  for  walking  or  jumping;    spiracles  of  abdomen  usually  ventral; 

beak  segmented, 
b.  Apex  of  head  usually  directed  anteriorly ;  beak  arising  from  its  apex;  sides 
of  the  face  remote  from  the  front  coxae;   first  pair  of  wings  when  present 
thickened   at   base,    with    thinner   margins HETEROPTERA 


159. 


Taxonomic  details  of  Hemiptera-Heteroptera.      (a)   Dorsal  aspect;    (b)  seta  from 
bedbug;   (c)  wing  of  Heteropteron;    {d)  leg;    (e)  wing  of  Sinea. 


c.  Front  tarsi  of  one  segment,  spade-form   (palseformes) ;    beak  short,  at 
most  two-segmented;    intermediate  legs  long,  slender;    posterior  pair 

adapted    for    swimming CoRixiDiE 

cc.  Front  tarsi  rarely  one-segmented,  never  spade-form;   beak  free,  at  least 
three-segmented, 
d.  Pulvilli  wanting. 

e.  Hemelytra  usually  with  a  distinct  clavus  (fig.  159),  clavus  always 

ends  behind  the  apex  of  the  scuteUum,  forming  the  commissure. 

(Species  having  the  wings  much  reduced  or  wanting  should  be 

sought  for  in  both  sections.) 

f.  Antennae  very  short;    meso-  and  metastemum  composite;    eyes 

always  present. 


Siphtmculata  and  Hemiptera  277 

g.  Ocelli      present;       beak      four-segmented.        OcHTERiDiE  and 

Nerthrid^. 

gg.  Ocelli  wanting;   antennas  more  or  less  hidden  in  a  groove. 

h.  Anterior  coxaj  inserted  at  or  near  anterior  margin  of  the 

prostemum;    front  legs  raptorial;    beak  three-segmented. 

Belostomid.*;  (with swimming  legs),NEPiD^,NAUCORiD^. 

i.  Metasternum  without  a  median  longitudinal  keel;   antennae 

always  four  -segmented. 

j.  Beak  short,  robust,  conical;  the  hairy  fleck  on  the  corium 

elongate,  large,  lying  in  the  middle  between  the  inner 

angle  of  the  membrane  and  the  outer  vein  parallel  to 

the  membrane  margin;    membrane  margin  S-shaped. 

k.  The  thick  fore  femur  with  a  relatively  deep  longitudinal 

furrow    to    receive    the    tibia.     Several    American 

species  (fig.  19  f.) .  .  .Belostoma  ( =  Lethocerus  Mayer) 

kk.  The  less  thickened  fore  femur  without  such  a  furrow 

B.  griseus.   Benacus  Stal. 

jj.  Beak  slender,  cylindrical;    the  hairy  spot  on  the  corium 

rounded  lying  next  to  the  inner  angle  of  the  membrane. 

k.  Membrane  large,  furrow  of  the  embolium  broadened. 

Z.    aurantiacum,  fliiminea,    etc Zaitha 

kk.  Membrane    ver^^    short;     furrow    of    embolium    not 

broadened.     Western   genus Pedinocoris 

ii.  Metasternum  with  a  long  median  longitudinal  keel.     South- 
western forms Abediis  ovatus  and  Deniostoma  dilatato 

hh.  Anterior   coxae   inserted    at    the   posterior    margin    of    the 
prostemum;   legs  natatorial.     Back  swimmers  (fig.  19  b.) 

NOTONECTID.ffi; 

i.  Apices   of   the   hemelytra   entire;     the   three   pairs   of   legs 
similar  in  shape;    beak  three-segmented;    abdomen  not 

keeled  or  hairj^ Plea  Leach 

ii.  Apices  of  hemelytra  notched;    legs  dissimilar;    beak  four- 
segmented;    abdomen  keeled  and  hairy, 
j.  Hemelytra    usually    much    longer    than    the    abdomen; 
fourth  segment  of  the  antenna  longer  than  the  third 

segment;   hind  tarsi  with  claws Bueno  Kirk. 

jj.  Hemelytra  but  little  longer  than  the  abdomen;    fourth 
segment  of  the  antenna  shorter  than  the  third  seg- 
ment; hind  tarsi  without  claws  (fig.  19b) .  .  Notonecta  L. 
ff.  Antennae  longer  than  the  head;    or  if  shorter,  then  the  eyes  and 
ocelli  absent. 
g.  Eyes,   ocelli,  and  scutellum  wanting;    beak  three-segmented; 
head   short;    hemelytra   always   short;   membrane   wanting. 

Insects  parasitic  on  bats Polyctenid^ 

gg.  Eyes  present. 

h.  First  two  antennal  segments  ver>'  short,  last  two  long,  pilose, 
third  thickened  at  the  base;  ocelli  present,  veins  of  the 
hemelytra  forming  cells.  Dipsocorid/E  (  =  Ceratocombi- 
hje)  including  Schizopterid^. 


278  Hominoxious  Arthropods 

hh.  Third  segment  of  the  antenna  not  thickened  at  the  base, 

second  as  long  or  longer  than  the  third,  rarely  shorter. 

i.     Posterior  coxae  hinged  (cardinate),  if  rarely  rotating,  the 

ciineus  is  severed,  the  membrane  is  one  or  two-celled, 

and  the  meso-  and  metastemum  are  composite. 

j.  Ocelli  absent,  clypeus  dilated  toward  the  apex;  hemelytra 

always  short,  membrane  wanting.     3pecies  parasitic. 

Bed  bugs,  etc ClMICID^ 

k.  Beak    short,    reaching   to   about    the   anterior   coxae; 
scutellum  acuminate  at  the  apex;   lateral  margin  of 
the  elytra  but  little  refiexed,  apical  margin  more  or 
less    rounded;      intermediate    and    posterior    coxae 
very  remote. 
1.  Body  covered  with  short  hairs,  only  the  sides  of  the 
pronotum  and  the  hemelytra  fringed  with  longer 
hairs;    antennae    with    the  third  and  fourth  seg- 
ments very  much  more  slender  than  the  first  and 
second;    pronotum  with  the  anterior  margin  very 

deeply  sinuate Cimex  L. 

m.  Sides  of  the  pronotum  widely  dilated,  broader 
than    the    breadth   of   one    eye,    and    densely 
fringed  with   backward   curved  hairs;    apical 
margin  of  the  hemelytra  nearly  straight,  rounded 
toward  the  interior  or  exterior  angles, 
n.  Body  covered  with  very  short  hairs;    second 
segment  of  the  antenna  shorter  than  the  third; 
sides  of  the  pronotum  feebly  reflexed,  fringed 
with  shorter  hairs  than  the  breadth  of  one 
eye ;  hemelytra  with  the  commissural  (inner) 
margin  rounded  and  shorter  than  the  scutel- 
lum,   apical    margin    rounded    towards    the 
interior  angle.     The   common  bed  bug   (fig. 

igh) C.  lectularius  Linn 

nn.  Body  covered  with  longer  hairs;  second  and 
third  segments  of  the  antenna  of  equal 
length;  side  of  the  pronotum  narrowly,  but 
distinctly,  refiexed,  fringed  with  longer 
hairs  than  the  breadth  of  one  eye ;  hemelytra 
with  the  commissural  margin  straight  and 
longer  than  the  scutellum,  apical  margin 
rounded  towards  the  exterior  angle.  Species 
found  on  bats  in  various  parts  of  the  United 

States C.   pillosellus  Hov. 

mm.  Sides  of  the  pronotum  neither  dilated,  nor 
refiexed,  fringed  with  less  dense  and  nearly 
straight  hairs;  hemelytra  with  the  apical 
margin  distinctly  rounded.  Parasitic  on 
man,    birds    and    bats.     Occurs    in    the    old 

w'orld,  Brazil  and  the  West  Indies 

C.    hemipterus    Fabr.    (  =  rotundatus) 


Siphunculata  and  Heniiptera  279 

11.  Body  clothed  with  rather  longer  silky  hairs;    third 
and  fourth   segments  of  the  antenna  somewhat 
more  slender  than  the  first  and  second;    anterior 
margin  of  the    pronotum  very   slightly  sinuate  or 
nearly  straight  in  the  middle,  produced  at  the 
lateral  angles.     This  is  the  species  which  in  Ameri- 
can  collections  is  known  as   C.   hirundinis,   the 
latter  being  an  old  world  form.     It  is  found  in 
swallows    nests.     O.    vicarius .  .  .  .  Oeciacus    Slal 
kk.  Beak  long,  reaching  to  the  posterior  coxa;;   scutellura 
rounded  at  the  apex;   lateral  margins  of  the  elytra 
strongly   reflexed,   apical   margin    slightly   sinuate 
toward    the    middle;     intermediate    and    posterior 
coxae  sub-contiguous.     This  species  infests  poultry 
in   southwest   United   States  and   in   Mexico.     H. 
inodorus Hsematosiphon  Champ. 


160.  Pselliopsis  (Milyas) 
cinctus.  (x2).  After 
C.  V.  Riley. 

jj.  OcelU  present,  if  rarely  absent  in  the  female,  then  the 
tarsus  has  two  segments;  or  if  with  three  tarsal  seg- 
ments, the  wing  membrane  with  one  or  two  cells. 

k.  Beak  four-segmented,  or  with  two-segmented  tarsi. 
. .  IsoMETOPiD^,  MicROPHYSiD^  and  some  Capsid^e. 

kk.  Beak    three-segmented. 

I.  Hemelytra  with  embolium;     head  horizontal,  more 

or  less  conical;   membrane  with  one  to  four  veins, 

rarely  wanting ANTHOCORID.a; 

Several  species  of  this  family  affecting  man  have 
been  noted,  Anthocoris  kingi  and  congolense, 
from  Africa  and  Lyctocoris  campestris  from 
various  parts  of  the  world.  Lyctocoris  fitchii 
Reuter  (fig.  19  j),  later  considered  by  Reuter  as 
a  variety  of  L.  campestris,  occurs  in  the  United 
States. 

II.  Hemelytra  without  embolium.     Superfamily  Acan- 

THioiDEA     (  =  Sald^     Fieber     and     Leptopod^ 
Fieber) 


28o  Hominoxious  Arthropods 

ii.  Posterior  coxae   rotating. 

j.  Claws  preapical ;  aquatic  forms.     Gerrid.i;  and  Veliad.^ 
]].  Claws  apical. 

k,  Prosternum    without    stridulatory    sulcus    (notch    for 
beak). 

I.  Tarsus  with  three  segments;   membrane  with  two  or 

three  longitudinal  cells  from  which  veins  radiate; 
10^  rarely  with  free  longitudinal  veins  (Arachnocoris) 

or    veins    nearly    obsolete    (Arbela);     clavus    and 

corium  coriaceous;    ocelli  rarely  absent.  .Nabid.^; 

Reduviolus  (  =  Coriscus)  subcoleoptratus  (fig.  19  g), 
a  species  belonging  to  this  family,  occurring  in 
the  United  States,  has  been  accused  of  biting 
man.  This  insect  is  fiat,  of  a  jet  black  color, 
bordered  with  yellow  on  the  sides  of  the  abdomen, 
and  with  yellowish  legs.  It  is  predaceous, 
feeding  on  other  insects. 

II.  With   other   combinations   of   characters.     Hydro- 

METRID.E,  HeNICOCEPH.\LID^,  N.«0GEID/E,  MeSO- 
VELIAD^,  JoPPEICID.^ 

kk.  Prosternum  with  stridulatorj'  sulcus  (notch  for  beak) ; 
with  three  segments,  short,  strong. 

I.  Antennae  filiform  or  sometimes  more  slender  apically, 

geniculate;  wing  membrane  with  two  or  three 
large   basal   cells;     scutellum   small   or   moderate 

REDUVnD.ffi 

For  a  key  to  the  genera  and  species  see  next  page. 

II.  Last  antennal  segment  clav^te  or  fusiform;    wing 

membrane  with  the  veins  often  forked  and  ana- 
stomosing; scutellum  large;  tarsi  each  with  two 
segments;      fore     legs     strong.     (  =  Phymatid^) 

Macrocephalid.^ 

ee.  Clavus  noticeably  narrowed   towards  the  apex,   never  extending 

beyond  the  scutellum,  the  two  not  meeting  to  form  a  commissure; 

head  horizontal,  much  prolonged  between  the  antennas,  on  each 

side  with  an  antennal  tubercle,  sometimes  acute;    ocelli  absent; 

meso-  and  metastemum  simple;    tarsi  each  with  two  segments; 

body    flattened    (fig.     19c).     Aradid.e,    including    Dysodiid^. 

dd.  Pulvilli  present  (absent  in  one  Australian  family  Thaumatocorid.'E 

in  which  case  there  is  a  membranous  appendage  at  the  tip  of  the 

tibia).     Capsidje  (  =  MlRID.ffi),*  Eotrechus  (in   family  Gerrid^), 

N^OGAIDiE,      TlNGITID^,       PlESMID^,     MvODOCHID^,       CORIZID^, 

Coreid^e,     Alydid^,     Pentatomid^,     Scutellerid^,     etc. 
bb.  Apex  of  head  directed  ventrally,  beak  arising  from  the  hinder  part  of  the 
lower  side  of  the  head;   sides  of  face  contiguous  to  the  front  coxje;   first 


♦Professor  C.  R.  Crosby  who  has  been  working  upon  certain  capsids  states  that  he  and  hi.s 
assistant  have  been  bitten  by  Lygus  pratensis,  the  tarnished  plant  bug,  by  Chlamydatus  associatus 
and  by  Orthotylus  flavosparsus,  though  without  serious  results. 


ReduviidcB  of  the  United  States  281 

pair   of   wings,    wlien   present,    of   uniform    thickness.     Cicadas,   scale 

insects,  plant  lice  (Aphids),  spittle-insects,  leaf  hoppers,  etc 

HOMOPTERA 

REDUVIIDiE    OF   THE    UNITED    STATES 

(Adapted  from  a  key  given  by  Fracker). 
a.  Ocelli  none;   wings  and  hemelytra  always  present  in  the  adults;   no  discodial 
areole  in  the  corium  near  the  apex  of  the  clavus.     Orthometrops  decor ata, 

Oncerotrachelus  acuminatus,  etc.,    Pennsylvania   and    south Sarcina 

aa.  Ocelli  present  in  the  winged  individuals;    anterior  coxae  not  as  long  as  the 
femora, 
b.  Hemelytra  ^vithout  a  quadrangular  or  discoidal  areole  in  the  corium  near 
the  apex  of  the  clavus. 
c.  Ocelli  not  farther  cephalad  than  the  caudal  margins  of  the  eyes;   segment 
two  of  the  antenna  single, 
d.  Thorax  usually  constricted  caudad  of  the  middle;  anterior  coxae  ex- 
ternally fiat  or  concave PiRATlNiE 

e.  Middle  tibiae  without  spongy  fossa,  head  long,  no  lateral  tubercle 

on  neck.     5.  stria,   Carolina,   111.,   Cal Sirthenia  Spinola 

ee.  Middle  tibiae  with  spongy  fossa;    fore  tibias  convex  above;    neck 
with  a  small  tubercle  on  each  side, 
f.  Apical  portion  of  anterior  tibiae  angularly  dilated  beneath,   the 

spongy  fossa  being  preceded  by  a  small  prominence 

Melanolestes    Stal 

g.  Black,  with  piceous  legs  and  antennas.     N.  E.  States  (fig.  19a) 

M.  picipes 

gg.  Sides,  and  sometimes  the  whole  dorsal  surface  of  the  abdomen 

red.     111.,  and  southward M.  abdominalis 

ff.  Tibiae  not  dilated  as  in  "f";    spongy  fossa  elongate;    metapleural 
sulci    close    to    the    margin.     R.    biguttatus    (fig.    22).     South 

Rasahus  A.  and  S. 

dd.  Thorax  constricted  in  the  middle  or  cephalad  of  the  middle;   anterior 
tarsi  each  three-segmented. 
e.  Apex  of  the  scutellum  narrow,  without  spines  or  with  a  single  spine 

REDUvnN.s; 

f .  Antennae  inserted  in  the  lateral  or  dorso-lateral  margins  of  the  head ; 

antenniferous  tubercles  slightly  projecting  from  the  sides  of  the 

head;    head  produced  strongly  cephalad;    ocelli  at  least  as  far 

apart  as  the  eyes. 

g.  Antennae  inserted  very  near  the  apex  of  the  head;    segments 

one  and  three  of  the  beak  short,  segment  two  nearly  four 

times  as  long  as  segment  one.     R.  prolixus.     W.  I 

Rhodnius  Stal 

gg.  Antennae  inserted  remote  from  the  vertex  of  the  head. 

h.  Body  slightly  hairy;  pronotum  distinctly  constricted;  angles 
distinct;  anterior  lobe  four-tuberculate,  with  the  middle 
tubercles  large  and  conical.  M.  phyllosoma,  large  species 
the  southwest Mecctis  Stal 


2S2  Hominoxious  Arthropods 

hh.  Bod}-  smooth,  margin  of  the  prouotum  sinuous,  scarcely 
constricted;     anterior    lobe    lined    with    little    tubercles 

Conorhinus  Lap. 

i.  Surface   of  the    pronotum  and    presternum  more  or  less 

grandular. 
j.  Eyes  small,  head  black;    body  ver>'  narrow,  a  fifth  as 
wide  as  long;    beak  reaches  the  middle  of  the  proster- 

num.     California C.  protractus 

jj.  Eyes  large,  head  fuscous;  body  at  least  a  fourth  as  wide 

as  long.     Southern    species C.   rubro^asciatiis 

ii.  Pronotum  and  prosternum  destitute  of  granules. 

j.  Border  of  abdomen  entirely  black  except  for  a  narrow 
yellowish   spot  at  the  apex  of  one  segment.     Texas 

C.  gerstaeckeri 

jj.  Border  of  abdomen  otherwise  marked. 

k.  Beak  slender,  joints  one  and  two  slightly  pilose,  two 
more  than  twice  as  long  as  one;  tubercles  at  the 
apical  angles  of  the  pronotum  slightly  acute,  conical. 
Md.  to  111.  and  south.     The  masked  bed  bug  hunter 

(fig.  71) C.  sanguisugus 

kk.  Beak  entirely  pilose,  joint  two  a  third  longer  than 
joint    one;     joint    one    much    longer    than    three; 
tubercles  at  the  apical  angles  of  pronotum  slightly 
elevated,  obtuse.     Ga.,  111.,  Tex.,  Cal.  .  C.  variegatus 
ii.  Antenna  inserted  on  top  of  the  head  between  margins,  close  to  the 
eyes;  antenniferous  tubercles  not  projecting  from  the  side  of  the 
head, 
g.  Anterior  lobe  of  the  pronotum  with  a  bispinous  or  bituberculate 
disc;     femora    unarmed.     S.    arizonica,    S.   bicolor.     South- 
western species Spiniger  Burm. 

gg.  Disc  of  pronotum  unarmed;  apex  of  scuteUum  produced  into 
a  spine;  ocelli  close  to  the  eyes;  eyes  large  and  close  to- 
gether   Reduvius  Lamarck 

h.    Color    piceous.     Widely   distributed   in    the  United  States. 

(Fig.  20) R.    personatus 

hh.  More    or    less    testaceous    in    color.     Southwestern    states 

R.    senilis 

ee.  Apex  of  scuteUum  broad,  with  two  or  three  spines .  .  Ectrichodiin.^ 
f .  First  segment  of  the  antenna  about  as  long  as  the  head.     E.  cruciata 

Pa.  and  south;  E.  cinctiventris,  Tex.  and  Mex   

Ectrichodia  L.  et  S. 

ff.  First   segment   of    the   antennae   short.     P.    ceneo-nitens .      vSouth 

Pothea  A.  et  S. 

cc.  Ocelli  cephalad  of  the  hind  margins  of  the  eyes;  first  segment  of  the 
antennas  stout,  second  segment  divided  into  many  smaller  segments. 
South  and  west.  Homalocoris  maculicollis,  and  Hanimatocerus 
ptircis Hammatocerin^ 


ReduviidcB  of  the  United  States      ^  283 

bb.  Hemelytra  with  a  quadrangular  ordiscoidal  areole  in  the  corium  near  the 

apex  of  the  clavus  (fig.  I59e). 

c.  Anal  areole  of  the  membrane  not  extending  as  far  proximad  as  the  costal 

areole;    basal  segment  of  the  antenna  thickened,  porrect;    the   other 

segments  slender,  folding  back  beneath  the  head  and  the  first  segment 

StenopodiN/E 

d.  Head  armed  with  a  ramous  or  furcate  spine  below  each  side,  caudad 
of  the  eyes, 
e.  First  segment  of  the  antenna  thickened,  apex  produced  in  a  spine 
beyond  the  insertion  of  the  second  segment.     Species  from  Va., 

111.  and  south Pnirontis  Stal. 

ee.  First  segment  of  the  antenna  not  produced  beyond  the  insertion 

of  the  second  segment.     Pygolampis,   N.  E.   states  and  south; 

Gnathobleda,  S.  W.  and  Mex. 

dd.  Head  unarmed  below  or  armed  with  a  simple  spine;    rarely  with  a 

subfurcate  spine  at  the  side  of  the  base.     Carolina,  Missouri  and 

south.     Sienopoda,  Schumannia,   Diaditus,  Narvesus,    Oncocephalus 

CO,  Anal  areole  of  membrane  extending  farther  proximad  than  the  costal 

areole. 

d.  Ocelli  farther  apart  than  the  eyes.     A.  crassipes,  widely  distributed 

in  the  United  States;    other  species  occur  in  the  southwest 

Apiomerus  Hahn. 

dd.  Ocelli  not  so  far  apart  as  the  eyes ^ Zelin^ 

e.  Sides  of  mesostemum  without  a  tubercle  or  fold  in  front. 

f.  Fore  femur  as  long  as  or  longer  than  the  hind  femur;  first  segment 

of  the  beak  much  shorter  than  the  second.     Z.  audax,  in  the 

north  eastern  states;   other  species  south  and  west.  .Zelus  Fabr. 

ff.  Fore  femur  shorter  than  the  hind  femur,  rarely  of  equal  length, 

in  this  case  the  first  segment  of  the  beak  as  long  or  longer  than 

the  second. 

g.  First  segment  of  the  beak  shorter  than  the  second;   fore  femur 

a  little  shorter  than  the  hind  femur;   the  first  segment  of  the 

beak  distinctly  longer  than  the  head  before  the  eyes.     P. 

cinctiis  a  widely  distributed  species  (fig.  160).     P.  punctipes, 

P.   spinicoUis,    Cal.,    Mex {=  Milyas)  Psellioptis  Berg. 

gg.  First  segment  of  the  beak  as  long  or  longer  than  the  second, 
h.  Pronotum  armed  with  spines  on  the  disc. 

i.  Juga  distinctly  prominent  at  the  apex  and  often  acute  or 
subacute;  fore  femur  distinctly  thickened;  hemelytra 
usually  not  reaching  the  apex  of  the  abdomen.  Fitchia 
aptera,  N.  Y.,  south  and  west;  F.  spinosula,  South; 
Rocconata  annulicorttis,  Texas,  etc. 
ii.  Juga  when  prominent,  obtuse  at  apex;  eyes  full  width  of 
the  head ;  fore  femur  not  thickened ;  pronotum  with  four 
spines  on  posterior  lobe.     R.  taurus,  Pa.,  south  and  west 

Repipta  Stal. 

hh.  Pronotum  unarmed  on  the  disc. 


Hominoxiotts  A  rthropods 

i.     Spines  on  each  apical  angle  of  the  penultimate  abdominal 
segment.     A .  cinereus,  Pa.,  and  south .  .  Atrachelus  A.  et  S. 
ii.  Apical  angle  of  the  penultimate  abdominal  segment  un- 
armed.    Fitchia    (in    part);     Castolus     ferox,     Arizona, 
ee.  vSides  of  the  mesosternum  with  a  tubercle  of  fold  in  front  at  the  hind 
angles  of  the  prostemum;   first  segment  of  the  beak  longer  than 
the  part  of  the  head  cephalad  of  the  eyes, 
f.  Fore  femur  thickened,  densely  granulated;    hind  femur  unarmed. 


4eX 


f^mpoaiunn 
PuU/Uus- 


161.  Taxonomic  details  of  Diptera.  (a)  Ventral  aspect  of  abdomen  of  Cynomyia; 
(6)  antenna  of  Tabanus;  (c)  ventral  aspect  of  abdomen  of  Chortophila;  \d) 
ventral  aspect  of  abdomen  of  Stomcxys;  (e)  claw  of  Aedes  (Cule.xl  sylves- 
tris,  male;  (/)  claw  of  Hippoboscid;  (g)  foot  of  dipterous  insect  showing 
empodimm  developed  pulvilliform;  ijn)  hind  tarsal  segment  of  Simulium 
vittatum,  female;   (t)  foot  of  dipterous  insect  showing  bristle-like  empodium. 


g.  Fore  tibiae  each  with  three  long  spines  on  the  ventral  side. 
5'.   diadema    (fig.    I59e),  a  widely  distributed   species;    and 

several  southwestern  species Sinea  A.  et  S. 

gg.  Fore    tibiae    unarmed.     A.    multispinosa,    widely    distributed; 

A.  tabida,  Cal Acholla  Stal. 

.  Fore  femur  unarmed,  rarely  a  little  thickened,  a  little  granulated. 

g.  Pronotum  produced  caudad  over  the  scutellum,  with  a  high 

mesal  tuberculate  ridge  (fig.   ige).     A.  cristatus.     X.  Y.  to 

Cal.   and   south Arilus   Halin. 

gg.  Caudal  lobe  of  the  pronotum  six  sided,  neither  elevated  nor 
produced  caudad.  H.  americanus,  Southwest;  also  several 
W.   I.   and   Mexican  genera Harpactor  Lap. 


Dipiera 


285 


DIPTERA  (Mosquitoes,  Midges.  Flies) 

a.  Integument  leathery,  abdominal  segments  indistinct;    wings  often  wanting; 

parasitic  forms PUPIPARA 

b.  Head  folding  back  on  the  dorsum  of  the  thorax;    wingless  flies  parasitic 

on  bats.     Genus  Nyderibia NvcTERiBiiDiE 

bb.  Head  not  folding  back  upon  the  dorsum  of  the  thorax;  flies  either  winged 
or  wingless;  parasitic  on  birds  and  on  bats  and  other  mammals. 
c.  Antennae  reduced,  wings  when  present,  with  distinct  parallel  veins  and 
outer  crossveins;  claws  simple;  palpi  leaf -like,  projecting  in  front  of 
the  head.  Flies  chiefly  found  on  bats.  Several  genera  occur  in  North 
America    Streblid^ 


162.     Hippobosca  equina.     X4.     After  Osborn. 

cc.  Antenna;  more  elongate,  segments  more  or  less  distinctly  separated; 
head  sunk  into  an  emargination  of  the  thorax;  ^^•ings  when  present 
with  the  veins  crowded  toward  the  anterior  margin;  palpi  not  leaf- 
like   HiPPOBOSCica; 

d.  Wings  absent  or  reduced  and  not  adapted  for  flight. 

e.  Wings  and  halteres  (balancers)  absent.     M.  oviniis,  the  sheep  tick 

Melophagus   Latr. 

ee.  Wing  reduced  (or  cast  off),  halteres  present, 
f.  Claw  bidentate;   ocelli  present.     On  deer  after  the  wings  are  cast 

off.     L.  depressa Lipoptena   Nitsch 

ff.  Claw   tridentate    (fig.    161    f) On  Macropis.     B.  femorata 

Brachypteromyia  _  Will. 

dd.  Wings  present  and  adapted  for  flight. 
e.  Claws  bidentate. 

f.  Ocelli  present;    head  flat;    wings  frequently  cast  off.     On  birds 

before    casting   of   the   wing Lipoptena    Nitsch. 

ff.  Ocelli    absent;     head    round;     wings   present.     The    horse    tick 

H.  equina  may  attack  man  (fig.   162) Hippobosca  L. 

ee.  Claws  tridentate  (fig.  161  f.). 
f.  Anal  cell  closed  at  apical  margin  by  the  anal  crossvein. 

g.  Ocelli     absent Stilbometopa     Coq . 

gg.  Ocelli  present. 


286  Hominoxious  Arthropods 

h.  R4-t-5  does  not  form  an  angle  at  the  crossvein.  On  birds. 
There  is  a  record  of  one  species  of  this  genus  attacking  man 

Omithomyia  Latr. 

hh.  R4  +  S     makes    an    angle    at    the    crossvein.     O.    confitiens, 

Ornithoica  Rdi. 

ff.  Anal  cell  not  closed  by  an  anal  crossvein.     Lynchia,  Pseudolfersia, 
and  Olfersia  are  chiefly  bird  parasites.     The  first  mentioned 
genus  is  said  to  be  the  intermediate  host  of  Hamoproteus  columbce. 
aa.  Abdominal  segments  chitinous;   not  parasitic  in  the  adult  stage. 

b.  Antenna  with  sLx  or  more  segments  and  empcdium  not  developed  pulvilli- 
form;   palpi  often  with  four  segments. 
c.  OcelH  present.     Blepharocertd^,   Rhyphid^e,    BiBiONiDiE,    Myceto- 

philiDjE,  besides  some  isolated  genera  of  other  families, 
cc.  Ocelli  absent. 

d.  Dorsum  of  the  thorax  with  a  V-shpaed  suture;    wings  usually  with 
numerous  veins;    legs  often  very  long  and  slender.     Crane  flies. 

TlPULID^ 

dd.  Dorsum  of  the  thorax  without  a  V-shaped  suture. 

e.  Not  more  than  four  longitudinal  veins  ending  in  the  wing  margin; 
wing  usually  hairy:  antennae  slender;  coxae  not  long;  tibiae  with- 
out spurs,  legs  long  and  slender.     Small,  delicate  flies  often  called 

Gall  gnats Cecidomyiid^ 

ee.  More  than  four  longitudinal  veins  ending  in  the  wing  margin, 
f .  The  costal  vein  is  not  produced  beyond  the  tip  of  the  wing ;  radius 
with  not  more  than  three  branches, 
g.  Antennae  short,  composed  of  ten  or  eleven  closely  united  seg- 
ments;   legs  stout;    body   stout;    abdomen  oval;    anterior 
veins  stout,  posterior  ones  weak  (fig.  163  b);  eyes  of  the  male 
contiguous    over    the    antennae.     Black    flies,    buffalo    flies, 
turkey   gnats.     Many    North   American   species,    several   of 

them   notorious  for   their  blood   sucking   propensities 

SlMULnD.ffi 

h.  Second  joint  of  the  hind  tarsus  with  basal  scale-like  process  and 
dorsal  excision  (fig.  161  h);  radial  sector  not  forked;  no 
small  cell  at  the  base  of  the  wing.  S.  forbesi,  jenningsi, 
johannseni,   meridionale,   piscicidium,  venustum,  vittatum, 

etc.     Widely  distributed  species 

( =Eusiinulium)  Simulium  Latr. 

hh.  No  basal  scale-like  process  on  the  second  joint  of  the  hind 

tarsus;   radial  sector  usually  forked  (fig.  163  b). 

i.  Face  broad,  small  basal  cell  of  the  wing  present.     P.fulvum, 

hirtipes,  mutatum,  pecuarum,  pleurale .  .  Prosimulium  Roub. 

ii.  Face  linear;    small  basal  cell  of  the  wing  absent.     One 

species,  P.  ftircatum,  from    California 

Parasimulium  Malloch 

gg.  Flies  of  a  different  structure. 

h.  Antennae  composed  of  apparently  two  segments  and  a  terminal 
arista  formed  of  a  number  of  closely  imited  segments. 
Rare    flies    with    aquatic    larvae Orphnephilid^e 


Diptera  287 

hh.  Antennae  of  six  to  fifteen  segments,  those  of  the  male  usually 
plumose;     legs    frequently    slender    and    wings    narrow 

Chironomid^ 

i.  Media  forked  (except  in  the  European  genus  Br  achy  pogon); 
thorax  without  longitudinal  fissure  and  not  produced  over 
the  head  (except  in  four  exotic  genera);  antenna;  usually 
fourteen-jointed  in  both  sexes;  fore  tibia  with  a  simple 
comb  of   setulae,   hind  tibia  with  two  unequal   combs, 

middle  tibia  without  comb CERATOPOGONIN^ 

j.  Thorax  produced   cap-like  over  the  head,   wing  narrow 
and    very    long.     Jenkinsia,    Macroptilum    and    Caly- 
ptopogon,    eastern   hemisphere;    Paryphocontis,    Brazil. 
jj.  Thorax  not  produced  over  the  head. 

k.  Eyes  pubescent,  empodium  well  developed,  or  if  short 
then  R2-1-3  distinct  and  crossvein-like  or  the 
branches  of  R  coalescent;  r-m  crossvein  present; 
fore  femora  not  thickened;  wing  either  with  ap- 
pressed    hairs    or    with    microscopic    erect    setulae 

Dasyhelea  Kieff. 

kk.  Eyes  bare,  or  otherwise  differing  from  the  foregoing. 

I.  Empodium   well   developed,   nearl}'   as   long   as   the 

claws  and  with  long  hairs  at  the  base;  femora  and 

fifth  tarsal  segments  unarmed,  i.e.  without  spines 

or  stout  setse;    fourth  tarsal  segment  cylindrical. 

m.  Wing  with  erect  and  microscopic  setulae.     Widely 

distributed 

( =  Atrichopogon)    Ceralopogon    Meig. 

mm.  Wing  with  long  and  depressed  hairs.     Wideh* 

distributed Forcipomyia 

n.  Hind  metatarsus  shorter  or  not  longer  than  the 
following    (i.e.    the   second    tarsal)    segment 

*. Subgenus  Prohelea  Kieff 

nn.  Hind   metatarsus   longer   than   the   following 
segment ....  Subgenus     Forcipomyia    Meig. 

II.  Empodium  short,  scarcely  reaching  the  middle  of 

the  claws,  or  vestigial, 
m.  R-m  crossvein  wanting. 

n.  Palpi  four  segmented ;  inferior  fork  of  the  media 

obliterated  at  the  base.     Australia 

Leptoconops  Skuse 

nn.  Palpi  three-segmented. 

o.  Legs  spinulose,  tarsal  claw's  of  the  female 
with  a  basal  tooth  or  strong  bristle,  those 
of  the  male  unequal,  the  anterior  with  a 
long  sinuous  tooth,   the  posterior  with  a 

short    arcuate     tooth.     Italy 

Mycterotypus  No^ 


288  Hominoxious  Arthropods 


oo.  Legs   unarmed;     no   crossvein   between   the 
branches  of  the  radius  (fig.   i63e).     New 

Mexico Tersesthes  Townsend 

mm.  R-m  crossvein  present. 

n.  Fore  femora  very  much  swollen,  armed  with 

spines  below,  fore  tibia  arcuate  and  applied 

closely  to  the  inferior  margin  of  the  femur. 

o.  R24-3  present,  therefore  cell  Ri  and  R2  both 

present;     wing    usually    fasciate.     United 

States Heleromyia  Say. 

00.  R2+3   not   distinct    from  R4  +  S,    hence   cell 

R3  obliterated.     South  America 

Pachyleptus  Arrib.  (Walker) 

nn.  Fore  femur  not  distinctly  swollen. 

o.  R2  +  3   present     therefore    cells    Ri   and    R3 

both  present,  or  if  not,  then  the  branches 

of    the    radius    more    or    less    coalescent, 

obliterating  the  cells. 

p.  At  least  the  tip  of  the  wing  with  erect 

setulae;    tip  of   R4+5  scarcely   attaining 

the  middle  of  the  wing,  empodium  rather 

indistinct,  not  reaching  the  middle  of  the 

claws,  the  claws  not  toothed,  equal,  with 

long  basal   bristle;    legs  without    stout 

setae.     Widely     distributed 

Culicoides  Latr, 

Haematomyidium  and  Oecacta  are  prob- 
able synonyms  of  this. 
pp.  Wings  bare,  if  rarely  with  hair,  then  the 
radius  reaches  beyond   two-thirds  the 
length  of  the   wing,   or  the  femur  or 
•  fifth  tarsal  segment  with  stout  black 

spines. 

q.  Media    unbranched.     Europe 

Brachypogon    Kieff 

qq.  Media  branched. 

r.  Hind  femur  much  swollen  and  spined. 
America  and  Europe .  Serroniyia  Meg. 
rr.  Hind    femur    not    distinctly    swollen. 
s.  Cell  Ri  not  longer  than  high;    fork 
of  the  media  distad  of  the  cross- 
vein;    wing  with  microscopic  setu- 
lae   Stilobezzia  Kieff 

ss.  Cell  Ri  elongate. 

t.  Femora     vmarmed.     Widely     dis- 
tributed.   ( =  Sphaeromias  Kieff. 

1913    not    Curtis?) 

Johannseniella  Will. 


Dipt  era  289 

tt.  Femora,    at   least   in    part,    with 
strong    black    spines.     Widely 
distributed .  Palpomyia  Megerle 
00.   R2+3  coalescent   with  R4+5  hence    cell  R3 
is  obliterated. 
p.  In    the   female    the   lower   branch   of   the 
media  with  an  elbow  near  its  base  pro- 
jecting   proximad,    the    petiole    of    the 
media  coalescent  with  the  basal  section 
of    the  radius,   wing    long   and  narrow, 
radial  sector  ending  near  the  tip  of  tlie 
wing;  venation  of  the  male  as  in  Bezzia; 

front    concave.     United    States 

Stenoxenus     Coq. 

pp.  Venation  otherwise,  front  not  concave, 
q.  Subcosta  and  Ri  more  or  less  coalescent 
with  the  costa;  wing  pointed  at  the 
apex,  much  longer  than  the  body; 
antennae  fourteen  segmented,  not  plu- 
mose.    India Haasiella  Kiefl, 

qq.  Subcosta  and  radius  distinct  from  the 
costa. 
r.  Abdomen    petiolate .  . .  Dibezzia    Kieff . 
rr.  Abdomen    not    petiolate. 

s.  Head  semi-globose;  hind  tarsi  un- 
usually elongate  in  the  female; 
antennae  of  the  male  not  plumose. 

Europe Macropeza    Meigen. 

ss.  Head  not  globose,  more  or  less 
flattened  in  front;  antennae  of 
the  male  plumose.  Widely  dis- 
tributed  Bezzia     Kieflf. 

t.  Fore  femora,  at  least,  armed  with 

stout  spines  below 

Subgenus    Bezzia    Kieflf. 

tt.  Femora   unarmed 

.  .  .  .Subgenus   Probezzia  Kieflf. 
ii.  Media  of  the  wing  simple,  and  otherwise  not  as  in  "i".     To 
this  group  belong  numerous  Chironomid  genera,  none  of 
which  are  known  to  be  noxious  to  man. 
ff.  The  costal  vein  apparently  is  continued  arovmd  the  hind  margin  of 
the  wing;   radius  with  at  least  four  branches. 
g.  Wing  ovate  pointed,  with  numerous  veins;    crossveins,  if  evi- 
dent, before  the  basal  third  of  the  wing;    veins  verj'  hairy; 

very  small  moth-like  flies PSYCHODID.aE 

h.  With  elongate  biting  proboscis;  the  petiole  of  the  anterior 
forked  cell  of  the  wing  (R2)  arises  at  or  beyond  the  middle  of 
the  wing  (fig.  163d) Phlebotomus  Rdi. 


290 


Hominoxious  Arthropods 


163.  Wings  of  Diptera.  (a)  Anopheles;  (6)  Prosimulium ;  (c)  Johannseniella;  [d)  Phle- 
botomus  (After  Doerr  and  Russ);  (e)  Tersesthes  (after  Townsend);  (/)  Ta- 
banus;  (g)  Symphoromyia;  (h)  Aphiochaeta;  (t)  Enstalis;  (j)  Gastrophilus; 
(k)  Fannia;    (f)  Musca. 


Dipt  era  291 

hh.  With  shorter  proboscis;    the  petiole  of  the  anterior  forked 

cell  arises  near  the  base  of  the  wing 

Psychoda,  Pericoma,  etc. 

gg.  The  r-m  crossvein  placed  at  or  beyond  the  center  of  the  wing; 

wings  not  folded  roof -like  over  the  abdomen. 

h.  Proboscis  short,  not  adapted  for  piercing;   wings  bare  (Dixi- 

vim);    or   wings   scaled    (Culicid,«,    Subf.    Corethrin^). 

hh.  Proboscis   elongate,    adapted    for    piercing;     wings    scaled, 

fringed  on  the  hind  margin;    antennae  of  the  male  bushy 

plumose.     Mosquitoes 

CULlciD.ffi;  (exclusive  of  Corethrin^) 

i.  Metanotum  without  setae. 

j.  Proboscis  strongly  decur\'ed;  body  with  broad,  ap- 
pressed,  metalescent  scales;  cell  R2  less  than  half  as 
long  as  its  petiole;  claws  of  female  simple,  some  of  the 
claws  of  the  male  toothed.  Several  large  southern 
species   believed    to   feed   only   on   nectar   of   flowers 

Megarhinns  R.  D. 

ij.  Proboscis  straight  or  nearly  so,  or  otherwise  different, 
k.  Scutellum  evenly  rounded,  not  lobed;   claws  simple  in 
both    sexes Anopheles     Meig. 

I.  Abdomen  with  clusters  of  broad  outstanding  scales 

along  the  sides;   outstanding  scales  on  the  veins  of 
the  wing  rather  narrow,  lanceolate;    upper  side  of 
the  thorax  and  scutellum  bearing  many  appressed 
lanceolate  scales.     Florida  and  southward  (Cellia) . 
m.  Hind  feet  from  the  middle  of  the  second  segment 
largely  or  wholly  snow  white. 
n.  With  a  black  band  at  the  base  of  the  last  seg- 
ment of  each  hind  foot 

A.  albimanus*  and  tarsimaculata* 

nn.  Without     such     a    band.  .  .  .A.     argyritarsis* 

mm.  Hind  feet  black,  mottled  with  whitish  and  with 

bands  of  the  sarae  color  at  the  sutures  of  the 

segments.     W.   I A.  maculipes 

II.  Abdomen  without  such  a  cluster  of  scales;  outstand- 

ing scales  of  the  wing  veins  rather  narrow,  lanceo- 
late; tarsi  wholly  black, 
m.  Deep  black,  thorax  obscurely  lined  with  violace- 
ous, especially  posteriorly;  head,  abdomen  and 
legs  black;  no  markings  on  the  pleura;  ab- 
domen without  trace  of  lighter  bandings; 
wing  scales  outstanding,  uniform,  not  forming 
spots,  though  little  thicker  at  the  usual  points 
indicating  the  spottings.     Florida.  .A.  atropus 


♦Species  marked  with  an  *  are  known  to  transmit  malaria.  Species  found  only  in  tropical 
North  America  and  not  known  to  carry  malaria  have  been  omitted  from  this  table,  but  all  found 
in  the  United  States  are  included. 


292  Hominoxious  Arthropods 


mm.  Otherwise  marked  when  the  wings  are  unspotted, 
n.  Wings  unspotted. 

o.  Petiole  of  the  first  forked  cell  (R2)  more  than  a 
third  the  length  of  the  cell.     Mississippi 

valley A.  walkeri 

00.  Petiole  of  the  first  forked  cell  a  third  the 

length  of  the  cell.     Md A.  barberi 

nn.  Wings  spotted. 

o.  Front  margin  of  the  wings  with  a  patch  of 

whitish  and  yellow  scales  at  a  point  about 

two-thirds  or  three-fourths  of  the  way  from 

base  to  apex  of  wing. 

p.  Veins  of  the  wing  with  many  broad  obovate 

outstanding  scales;    thorax  with  a  black 

dot  near  the  middle  of  each  side.     W.  I. 

A.  grabhami* 

pp.  The  outstanding  scales  of  the  wings  rather 

narrow,  lanceolate. 

q.  Scales  of  the  last  vein  of  the  wings  white, 

those  at  each  end  black;    R4+5  black 

scaled,  the  extreme  apex  white  scaled. 

Widely    distributed   north   and   south 

(fig.     131) A.     punctipennis 

A  dark  variety  from  Pennsylvania  has 
been    named    A.    perplexens. 
qq.  Scales  of  the  last  vein  of  the  wing  white, 
those  at  its  apex  black;    R4+5  white 
"    scaled     and     with     two    patches    of 
black  scales.     South  and  the  tropics. 
A.  franciscanus  and  pseudopunctipen- 
nis* 
00.  Front   margin   of    the   wings   wholly   black 
scaled, 
p.  Last  (anal)  vein  of  the  wings  white  scaled 
with  three  patches  of  black  scales  (fig. 
132).     New  Jersey  to  Texas .  .A.crucians* 
pp.  Last    vein    of    the    wings    wholly    black 
scaled, 
q.  Widely     distributed     north     and     south 

(fig.  130),  ( =maculipennis) 

A.     quadrimaculatus* 

qq.  Distributed     from     Rocky     Mountains 

westward A.  occidentalis 

kk.  Scutellum   distinctly    trilobed. 

L  Cell  R2  less  than  half  as  long  as  its  petiole;  thorax 
with  metallic  blue  scales;  median  lobe  of  the 
scutellum  not  tuberculate;  few  small  species  which 
are  not  common Uranotaenia  Arrib. 


Dipt  era  293 

11.  Cell  R2  nearly  or  quite  as  long  as  its  petiole,  or 
otherwise  distinct. 
m.  Femora  with  erect  outstanding  scales;    occiput 
broad  and  exposed.     Large  species.     P.  ciliata. 

P.howardi Psorophora  R.  D. 

mm.  Femora  without  erect  scales. 

n.  Clypeus  bearing  several  scales  or  hairs,  scutel- 
lum  with  broad  scales  only;  back  of  head 
with  broad  scales;  scales  along  the  sides  of  the 
mesonotum  narrow;  some  or  the  claws 
toothed;  thorax  marked  with  a  pair  of 
silvery  scaled  curved  stripes;  legs  black 
with  white  bands  at  the  bases  of  some  of  the 
segments  (fig.  134).     YeUow  Fever  mosquito 

Aedes  ( =  Stegomyia)  calopus. 

nn.  With     another     combination     of    characters. 

Numerous  species  of  mosquitoes  belonging 

to    several    closely    related    genera,    widely 

distributed  over  the  country.     (Culex,  Aedes, 

Ochlerotatus,  etc.).     Culex  in  the  wide  sense. 

ii.  IVIetanotum  with  setae.      Wyeomyia  (found  in  the  United 

States) ;    and   related  tropic  genera. 

bb.  Antennae  composed  of  three  segments  with  a  differentiated  style  or  bristle; 

third  segment  sometimes  complex  or  annulate,  in  which  case  the  empo- 

dium  is  usually  developed  like  the  pulvilli,  i.e.,  pad-like  (fig.   161  g). 

c.  Empodium    developed   pad-like    (pulvilliform)    i.e.,    three   nearly   equal 

membranous  appendages  on  the    underside  of  the  claws  (fig.  i6ig). 

d.  Squamae,  head,  and  eyes  large;    occiput  flattened  or  concave;    third 

segment  of  the  antennae  with  four   to  eight  annuli    or  segments, 

proboscis  adapted  for  piercing;    body  with  fine  hairs,  never  with 

bristles;    middle  tibia  with  two  spurs;     wing  venation  as  figured 

(fig.    i63f);     marginal    vein   encompasses  the  entire  wing.     Horse 

flies,  greenheads,  deer  flies,  gad  flies TABANID.ffi* 

e.  Hind  tibia  with  spurs  at  tip;  ocelli  usually  present   (PANGONIN.ffi) 
f.  Third   joint  of  the  ^.ntennse  with  seven  or  eight  segments;   probo- 
cis  usually  prolonged. 
g.  Each  section  the  the  third  antennal  segment  branched.     Central 

American  species,  P.  festce Pityocera  G.  T. 

gg.  Sections  of  the  third  antennal  segment  not  branched. 

h.  Upper  comer  of  the  eyes  in  the  female  terminating  in  an  acute 
angle;    wings  of  both  sexes  dark  anteriorly.  G.  chrysocoma, 

a  species  from  the  eastern  states Goniops  Aid. 

hh.  Upper  comer  of  the  eye  in  the  female  not  so  terminating; 

wings  nearly  uniform  in  color,  or  hyaline. 

i.  Proboscis  scarcely  extending  beyond  the  palpi;   front  of  the 

female   wide;     much   wider   below   than   above.     S.   W. 

States Apatolestes  Will. 


*This  table  to  the   North  American   genera  of  the  Tabanidae   is  adapted  from  one  given  by 
Miss  Ricardo. 


294  Hominoxious  Arthropods 

ii.     Proboscis  extending  beyond  the  palpi. 

j.  Wing  with  cell  M3  closed.     Tropic  America 

{=Diclisa)  Scione  Wlk. 

jj.  Cell  M3  open;    ocelli  present  or  absent.     Two  or  three 

eastern  species;  many  south  and  west.  .Pangonia  Rdi. 

ff.  Third  segment  of  the  antenna  with  five   divisions;   oceUi  present. 

g.  First  and  second  segments  of  the  antenna  short,  the  second  only 

half  as  long  as  the  first,  three  western  species.  .  .  .Silvius  Rdi. 

gg.  First  and  second  segments  of  the  antenna  long,  the  second 

distinctly  over  half  as  long  as  the  first.     Deer  flies.     Many 

species,    widely    distributed Chrysops    Meig. 

ee.  Hind  tibia  without  spurs;    ocelli  absent. 

f .  Third  segment  of  antenna  with  four  divisions,  no  tooth  or  angula- 
tion; wings  marked  with  rings  and  circles  of  darker  coloring; 
front  of  the  female  very  wide.     Widely  distributed.     H.  ameri- 

cana,     H.     punctulata Haematopota     Meig. 

ff.  Third   segment  of   the  antenna  with  five   divisions   (fig.    i6ib). 

g.  Third  segment  of  the  antenna  not  furnished  with  a  tooth  or 

distinct   angular   projection. 

h.  Body  covered  with  metallic  scales;  front  of  female  of  normal 

width;     front    and     middle     tibiae     greatly     dilated.     L. 

lepidota Lepidoselaga   Macq. 

hh.  Body  without  metallic  scales;  antennee  not  very  long,  the 
third  segment  not  cylindrical,  not  situated  on  a  projecting 
tubercle;      front     of     the     female     narrow.     South.      D. 

ferrugatus i=Diabasis)  Diachlorus  0.  S. 

gg.  Third  segment  of  the  antenna    furnished  with  a  tooth  or  a 
distinct  angular  projection, 
h.  Hind   tibiae    ciliate    with    long    hairs.     S.    W.  and    tropics. 

Snowiella  and  Stibasoma. 

hh.  Hind  tibias  not  ciliate. 

i.  Species  of  slender  build,  usually  with  a  banded  thorax  and 
abdomen;  third  segment  of  the  antenna  slender,  the 
basal    prominence   long;     wings    mostly    with   brownish 

markings.     Tropic    Anrierica Dichelacera    Macq. 

ii.  Species  of  a  stouter  build;  third  segment  of  the  antenna 
stout,  its  basal  process  short  (fig.  i6ib).     Many  species, 

widely  distributed Tabanus  L. 

dd.  With  another  group  of  characters. 

e.  Squamae  small,  antennae  variable,  thinly  pUose  or  nearly  bare  species, 
without  distinct  bristles;  wing  veins  not  crowded  anteriorly,  R4  and 
R5  both  present,  basal  cells  large;   middle  tibiae  at  least  with  spurs 

Leptid.* 

f.  Flagellum  of  the  antenna  more  or  less  elongated,  composed  of 
numerous  more  or  less  distinct  divisions 

XyLOPHAGIN^  and  ARTHROCERATINiE. 

ff.  Antennae  short,  third  segment  simple,  with  arista  or  style;   face 
small,  proboscis  short LEPTIN.ffl 


Diptera  295 

g.  Front  tibiae  each  with  one  or  two  spurs,  or  if  absent,  then  no 
discal   cell.     Triptolricha,   Pheneus,   Dialysis,    Hilarimorpha. 
gg.  Front  tibffi  without  terminal  spurs,  discal  cell  present. 
h.  Hind  tibae  each  with  a  single  spur. 

i.  Anal  cell  open  (fig.  i63g);  third  antcnnal  segment  kidney- 
shaped  with  do.rsal  or  subdorsal  arista;  first  antennal 
segment  elongate  and  thickened.  About  a  dozen  species 
have  been  described  from  the  United  States,  of  which  at 
least  one  (S.  pachyceras)  is  known  to  be  a  vicious  blood 

sucker Symphoromyia  Frauenf . 

ii.  Anal  cell  closed;  third  antenna]  segment  not  kidney- 
shaped Chrysopila,  Ptiolina,    Spania. 

hh.  Hind  tibiae  each  with  two  spurs. 

i.  Third  segment  kidney-shaped,  the  arista  subdorsal;  anal 

cell  closed Atherix  Meig. 

ii.  Third  segment  of  the  antenna  short  and  with  terminal 

arista;   anal  cell  open Leptis  Fabr. 

Two  European  species  of  this  genus  have  been  accused  of 
blood  sucking  habits,  but  the  record  seems  to  have 
been  based  upon  error  in  obser\^ation. 

ee.  With  another  combination  of  characters 

Stratiomyiid^,  Cyrtid^,  etc. 

cc.  Empodium  bristlelike  or  absent. 

d.  Antennae  apparently  two-segmented,  with  three-segmented  arista, 
wings  (rarely  wanting)  with  several  stout  veins  anteriorly,  the 
weaker  ones  running  obliquely  across  the  wing  (fig.  i63h);  small, 
quick  running,  bristly,  humpbacked  flies.     Several  genera;    Aphio- 

chaeta,  Phora.  Trineura,  etc PHORlD.ffi; 

dd.  Flies  with  other  characters. 

e.  No  frontal  lunule  above  the  base  of  the  antennas;  both  R4  and  R5 
often  present;  third  segment  of  the  antenna  often  with  a  terminal 
bristle.     AsiLlD.ffi,   Mydaid^e,  Apiocerid^,  Therevid^e,  Sceno- 

PINID^,      BOMBYLIID^,      EmPIDID^,     DOLICHOPODID^,     LONCHOP- 
TERID/E. 

ee.  A  frontal  lunule  above  the  base  of  the  antennae;  third  segment  of  the 

antenna  always  simple,   i.e.,  not  ringed,   usually  with  a  dorsal 

arista;   R4  and  R5  coalesced  into  a  simple  vein. 

f.  A  spurious  vein  or  fold  between  the  radius  and  the  media,  rarely 

absent;   the  cell  R4+5  closed  at  the  apex  by  vein  Mi;  few  or  no 

bristles  on  the  body,  none  on  the  head;    flies  frequently  with 

yellow  markings.     Eristalis   (fig.   1631),  Helophilus,  and  many 

other  genera SYRPHIDiE 

ff.  No  spurious  vein  present. 

g.  Body  without  bristles;    proboscis  elongate  and  slender,  often 
folding;    front  of  both  male  and  female  broad.  .  .  .Conopid^ 
gg.  Bristles  almost  always  present  on  head,  thorax,  abdomen  and 
legs. 


296  Hominoxious  Arthropods 

h.  Arista  terminal;    hind  metatarsus  enlarged,  sometimes  orna- 
mented, hind  tarsus  more  or  less  flattened  beneath 

PLATYPEZIDiE 

hh.  FUes  having  a  different  combination  of  characters. 

i.  Head  large,  eyes  occupying  nearlj-  the  entire  head;    cell 
R44-5  narrowed  in  the  margin;  small  flies  .  .PiPUNCULiDiE 
ii.  Head  and  eyes  not  unusually  large. 

j.  Squamae  (tegulae,  or  calyptrae,  or  alulae)  not  large,  often 
quite  small,  the  lower  one  lacking,  or  at  most  barely 
projecting  from  below  the  upper  one  (antisquama)  • 
front  of  both  male  and  female  broad,  the  ej^es  therefore 
widely  separated;  posthumeral  and  intraalar  macro- 
chaeta  not  simultaneously  present;  thorax  usually 
without  a  complete  transverse  suture;  postalar  callus 
usually  absent;  the  connectiva  adjoining  the  ventral 
sclerites  always  visible;  hypopleural  macrochaetae 
absent;  last  section  of  R4+5  and  Mi+o  with  but  few 
exceptions  nearly  parallel;  subcostal  vein  often  wanting 
or  vestigial  or  closely  approximated  to  Ri;  the  latter 
often  short,  basal  cells  small,  the  posterior  ones  often 
indistinct    or    wanting;     vibrissae    present    or    absent 

ACALYPTRATE  MUSCOIDEA 

k.  Subcosta  present,  distinctly  separated  from  Ri  at  the 
tip;  Ri  usually  ends  distad  of  the  middle  of  the 
wing;  the  small  basal  cells  of  the  wing  distinct. 

I.  A  bristle  (vibrissa)  on  each  side  of  the  face  near  the 

margin  of  the  mouth.  Cordylurid^,  Sepsid^, 
Phycodromid.e,   Heteroneurid.e,   Helomyzid.e. 

II.  No  vibrissas  present. 

m.  Head  nearly  spherical,  cheeks  broad  and  re- 
treating; proboscis  short;  the  cell  R5  closed  or 
narrowed  in  the  margin;  legs  very  long;  tarsi 
shorter  than  the  tibiae.  Calobata  and  other 
genera MlCROPEZID.*; 

mm.  Flies  with  another  combination  of  characters. 
Rhopalomerid.e,     Trypetid^,     Ortalid^, 

SciOMYZID.t. 

kk  Subcosta  absent  or  vestigial,  or  if  present,  then 
apparent!}'  ending  in  the  costa  at  the  point  where 
Ri  joins  it;  Ri  usually  ends  in  the  costa  at  or  before 
the  middle  of  the  wing. 

I.  Arista  long  plumose,  or  pectinate  above;   oral  vibris- 

sas present;  anal  cell  complete;  costa  broken  at 
the  apex  of  Ri.  Drosophila,  Phortica,  and  other 
genera Drosophilid.«; 

II.  With  another  combination  of  characters. 

m.  The  cell  M  and  first  M2  not  separated  by  a  cross- 
vein;    anal   cell   absent;     front   bare  or  only 


Diptera  297 

bristly    above;      usually    light     colored    flies. 
Hippelates,  Oscinus,  and   other  genera.     (See 

also  m  m  m OSCINID^ffi 

mm.  Cell  M  and  cell  first  M2  often  separated  by  a 

crossvein;  anal  cell  present,  complete,  though 

frequently  small;    scutellum  without  spines 

or    protuberances;      oral    vibrissse    present; 

arista  bare  or  short  plumose;  front  bristly  at 

vertex     only;      small     dark     flies.     Piophila 

(fig-  99).  Sepsis  and  other  genera.  .  .  Sepsid.* 

mmm.  The     Geomyzid/E,     Agromyzid.e,     Psilid.e, 

Trvpetid.^,  Rhopalomerid.e,  Borborid.'E 

and  DioPSiD.E  differ  in  various  particulars 

from  either  the  OSCINID.*;  and  the  SEPSID.S; 

noted  above. 

jj.  Squama-  well  developed,  usually  large,  the  lower  one 

frequently  projecting  from  below  the  upper  one;  both 

posthumeral     and     intraalar     macrochastag     present; 

thorax  with  a  complete  transverse  suture;    postalar 

callus  present  and  separated  by  a  distinct  suture  from 

the  dorsum  of  the  thorax;   front  of  the  female  broad, 

of  the  male  frequently  narrow,  the  eyes  then  nearly  or 

quite  contiguous;   the  connectiva  adjoining  the  ventral 

sclerites   either  visible   or   not;     hypopleural   macro- 

chsetae  present  or  absent;  subcosta  always  distinct  in 

its  whole  course,  Ri  never  short 

Calyptrate  Muscoidea* 

k.  Oral  opening  small,  mouth  parts  usually  much  reduced 
or  vestigial.  This  family  is  undoubtedly  of  poly- 
phyletic  origin  but  for  convenience  it  is  here  con- 
sidered as  a  single  family OESTRID.S;. 

1.  The  costal  vein  ends  at  the  tip  of  R4+5,  ^Ii+2 
straight,  not  reaching  the  wing  margin,  hence 
cell  R5  wide  open  (fig.  163J);  squamae  small; 
arista  bare;  ovipositor  of  the  female  elongate. 
Lar\'as   in   the   alimentary    canal   of   horses,    etc. 

Gastrophilus 

m.  Posterior     crossvein     (m-cu)     wanting;      wings 
smoky  or  with  clouds.     Europe.  .G.  pecorum 
mm.  Posterior  crossvein  (m-cu)  present,  at  least  in 
part. 

*The  classification  of  the  Muscoidea  as  set  forth  by  Schiner  and  other  earlier  writers  has 
long  been  followed,  although  it  is  not  satisfactory,  being  admittedly  more  or  less  artificial.  With- 
in the  last  two  or  three  decades  several  schemes  have  been  advanced,  that  of  Brauer  and  Bergen- 
stamm  and  of  Girschner,  with  the  modifications  of  SchnabI  and  Dziedzicki  having  obtained  most 
favor  in  Europe.  Townsend,  in  i90."<,  proposed  a  system  which  differs  from  Girschner's  in  some 
respects,  but  unfortunately  it  has  not  yet  been  published  in  sufficient  detail  to  permit  us  to  adopt 
it.  From  considerations  of  e.xpediency  we  use  here  the  arrangement  given  in  Aldrich's  Cata- 
logue of  Xorth  American  Diptera.  though  we  have  drawn  very  freely  upon  Girschner's  most  excel- 
lent paper  for  taxonomic  characters  to  separate  the  various  groups. 

It  may  sometimes  be  found  that  a  species  does  not  agree  in  all  the  characters  with  the  synop- 
sis;  in  this  case  it  must  be  placed  in  the  group  with  which  it  has  the  most  characters  in  common. 


298  Hominoxious  Arthropods 


n.  Wing  hyaline  with  smoky  median  cross  band, 

and  two  or  three  spots;  posterior  trochanters 

with  hook  in  the  male  and  a  prominence  in 

the  female.     World  wide  distribution.   G.  equi. 

nn.  Wings  without  spots. 

o.  Posterior  crossvein  (m-cu)  distad  of  the 
anterior  crossvein  (r-m) ;  legs,  particularly 
the  femora,  blackish  brown.     Europe  and 

North  America G.  haemorrhoidalis 

00.  Posterior  crossvein  opposite  or  proximad  of 
the  anterior  crossvein.     Europe  and  North 

America G.  nasalis 

11.  The  costal  vein  ends  at  the  tip  of  Mi    2,  M1+2  w-ith  a 

bend,  the  cell  R5  hence  much  narrowed  in  the 

margin,  or  closed. 

m.  Proboscis    geniculate,    inserted    in    a    deep    slit; 

female     without    extricate     ovipositor;     arista 

either  bare  or  plumose;   squamas  large;    facial 

grooves  approximated  below. 

n.  Arista  bare,  short.     Larvae  in  rodents.     Tropic 

America.     B.  princeps Bogeria  Austen 

nn.  Arista  pectinate  above. 

o.  Tarsi  broadened   and  flattened,  hair\%   anal 

lobe  of  the  wing  large.     Larvae  in  rodents. 

A  number  of  American  species.     Cuterebra. 

00.  Tarsi  slender,  not  hairy;    anal  lobe  of  the 

wing  moderate.     Larvae  in  man  and  other 

mammals.    Tropic  America.     D.cyaniven- 

tris Dermatobia  Br. 

mm.  Mouth  parts  very  small,  vestigial;   arista  bare, 

n.  Facial  grooves  approximated  below,  leaving  a 

narrow  median  depression  or  groove. 

o.  Cell   R5   closed   and   petiolate,    body   nearly 

bare.     Larvae  in  the  nasal  cavities  of  the 

smaller    Ungulates.     The    sheep    bot    fly. 

O.  ovis.     Widely  distributed ..  Oestrus  L. 

00.  Cell  R5  narrowly  open,  body  hairy.     Larvae 

parasitic  on  deer.     Europe  and  America 

Cephenomyia  Latr. 

nn.  Facial  grooves  far  apart,  enclosing  between 
them  a  broad  shield-shaped  surface;  squama; 
large;      female     with     elongate    ovipositor. 

Larvae    hypodermatic    on    Ungulates 

Hypoderma    Clark 

o.  Palpi  wanting;   tibiae  thickened  in  the  middle. 

p.  Hair  at  apex  of  the  abdomen  yellow;    legs 

including    femora    yellowish    brown .... 

H.    diana 


Dipt  era  299 

pp.  Hair  at  the  apex  of  the  abdomen  reddish 
yellow.     Europe  and  America, 
q.  Tibiae   and    tarsi   yellow;    femora    black 

H .  lineata 

qq.  Legs   black   with   black   hair;     tips   of 
hind  tibia  and  tarsi  yellowish  brown 

H.  bovis 

00.  Palpi    small,     globular;     tibiae    cylindrical, 

straight.     On    reindeer 0.    tarandi 

Oedemdgena   Latr. 

kk.  Oral  opening  of   the  usual   size;    mouth   parts  not 

vestigial. 

1.  Hypopleurals  wanting;    if  three  stemopleurals  are 

present    the    arrangernent    is     1:2;     conjunctiva 

(fig.   i6ic)  of  the  venter  usually  present;    if  the 

terminal  section  of  Mi+o  is  bent  it  has  neither  fold 

nor  appendage  (ANTHOMYIlD.ffi  of  Girschner). 

m.  Stemopleurals   wanting;    Mi-1-2   straight    toward 

the  apex,  costa  ends  at  or  slightly  beyond  the 

tip  of  R4+5;     mouth  parts  vestigial 

GASTROPHILIN.ffi.     See      OESTRID.S 

mm.  Stemopleurals  present,  if  rarely  absent  then 
differing  in  other  characters, 
n.  Caudal  margin  of  the  fifth  ventral  abdorpinal 
sclerite  of  the  male  deeply  notched  on  the 
median  line  usually  to  beyond  the  middle; 
abdomen  often  cylindrical  or  linear ;  abdomen 
often  with  four  to  eight  spots;  eyes  of  the 
male  usually  widely  separated;  stemo- 
pleurals three,  arranged  in  an  equilateral 
triangle;  subapical  seta  of  the  hind  tibia 
placed  very  low;  Mi-1-2  straight;  anal  vein 
abbreviated;  wings  not  rilled.  Ccenosia, 
Caricea,     Dexiopsis,     Hoplogaster,     Schosno- 

myia,  etc.     (Ccenosin^)* 

Anthomyiid.e  in  part 

nn.  Caudal  margin  of  the  fifth  ventral  abdominal 
sclerite  of  the  male  incurved,  rarely  deeply 
cleft,  rarely  en*"ire,  in  a  few  genera 
deeply  two  or  three  notched;    M1+2  straight 


♦There  are  several  genera  of  flies  of  the  family  Cordyluridce  (i.e.  Acalyptralce)  which  might  be 
placed  with  the  Anthomyiida  (i.e.  Calyptrata),  owing  to  the  relatively  large  size  of  their  squamae. 
As  there  is  no  single  character  which  will  satisfactorily  separate  all  doubtful  genera  of  these  two 
groups  we  must  arbitrarily  f^x  the  limits.  In  general  those  forms  on  the  border  line  having  a 
costal  spine,  or  lower  squama  larger  than  the  upper,  or  the  lower  surface  of  the  scutellum  more 
or  less  pubescent,  or  the  eyes  of  the  male  nearly  or  quite  contiguous,  or  the  eyes  hairy,  or  the 
frontal  setae  decussate  in  the  female;  or  any  combination  of  these  characters  may  at  once  be 
placed  with  the  Anthomyiidce.  Those  forms  which  lack  these  characteristics  and  have  at  least 
six  abdominal  segments  (the  first  and  second  segments  usually  being  more  or  less  coalescent) 
are  placed  with  the  .Acalyptrates.  There  are  other  acalyptrates  with  squamae  of  moderate  size 
which  have  either  no  vibrissae,  or  have  the  subcosta  either  wholly  lacking  or  coalescent  in  large 
part  with  R,,  or  have  spotted  wings;  they,  therefore  will  not  be  confused  with  the  calyptrates. 


300  Hominoxious  Arthropods 


or  curved ;  abdomen  usually  short  or  elongate 
oval;  stemopleurals,  if  three  are  present, 
arranged  in  the  order  i  :2  in  a  right  triangle. 
....  (MusciNiE-ANTHOMYiiN.^  of  Girschner) 
o.  Mi-i-2  straight,  hence  cell  R5  not  narrowed  in 

the  margin ANTHOMYirD.ffi  in  part 

p.  Underside  of  the  scuteUum  more  or  less 
sparsely  covered  with  fine  hairs;    anal 
vein    nearly    always    reaches    the    hind 
margin  of  the  wing;    extensor  surface  of 
the  hind  tibiae  with  a  number  of  stout 
setae;     squamae   often   small   and   equal. 
Anthomyia,      Chortophila,    Eustalomyia, 
Hammomyia,  Hylemyia,  Prosalpia,  Pego- 
myia,   etc.  .  .  .  HYLEMYIN^-PEG0MYIN.S; 
pp.  Underside   of   the   scuteUum   bare;     anal 
vein  does  not  reach  the  wing  margin, 
q.  First  anal  vein  short,  second  anal  sud- 
denly flexed  upwards;   hind  tibiae  each 
with  one    or    two  strong  setae  on  the 
extensor  surface.     Fannia  (  =  Homalo- 
myia),      Coelomyia,    Choristonia,    Eur- 
yomnia,  Azelia,  etc.  FANNIN.aE-AZELIN.a; 
qq.  Anal  veins  parallel  or  divergent. 

r.  Setae  on  the  exterior  surface  of  the  liind 
tibiae  wanting  (except  in  Limnaricia 
and  Ccenosites),  lower  squama  not 
broadened  to  the  margin  of  the 
scuteUum.  Leuco?nelina,  Limno- 
phora,  Limnospila,     Lispa,  Mydaea, 

Spilogaster,  etc 

Myd.«;in^-Limnophorin^ 

rr.  One  (rareh'  more)  seta  on  the  extensor 

surface  of  the  hind  tibia;    squamae 

usually  large  and  unequal.     Hydro- 

taea,     Aricia,     Drymeia,     Ophyra, 

Phaonia      {=Hyetodesia),     Pogono- 

myia,  Trichophthicus,  etc.   ARICINiE 

00.  Mi+2  cHirv'ed  or  bent,  hence  the  ceU  R5  more 

or    less     narrowed       in        the      margin. 

(MUSCINiE).     MUSCID.*:      in    part.     See 

page  303  for  generic  synopsis. 

U.  Hypopleurals   present;     when    three    stemopleurals 

are    present    the    arrangement    is    2:1    or    i:i:i. 

(TACHiNiDiE  of  Girschner) 

m.  Conjunctiva  of  the  ventral  sclerites  of  the  ab- 
domen present,  frequently  well  developed, 
surrounding  the  sclerites. 


Diptera  301 

n.  Mouth   parts  vestigial.     OESTRlDiE.     See  page 

297  for  generic  synopsis, 
nn.  Mouth  parts  well  developed. 

o.  Mi+2  straight,  hence    cell  R5  wide  open  in 
the  margin;   costa  ending  at  the  tip  of  R5; 
three     stemopleurals     present;      antennal 
arista    plumose.      Syllegoplera.        Europe. 
....  (Syllegopterin^e)  .  .  Dexiid.e  in  part 
00.  Mi-f2  bent,  hence  cell    R5  narrowed  in  the 
margin;     stemopleurals    rarely    wanting, 
usually   i:i  or  0:1 ;    facial  plate  strongly 
produced   below   vibrissal   angle  like   the 
bridge  of  the  nose;    antennal  arista  bare. 
Parasitic  on   Hemiptera  and  Coleoptera. 
AUophora,      Cistogasler,     Clytia,     Phasia, 
etc.      (Phasiin^).  .Tachinid.^     in    part, 
mm.  Conjunctiva  of  the  ventral  sclerites  invisible 
(fig.   i6ia). 
n.  Second  ventral  sclerite  of  the  abdomen  lying 
with  its  edges  either  upon  or  in  contact  with 
the    ventral    edges    of    the    corresponding 
dorsal  sclerite. 
o.  Outermost  posthumeral  almost  always  low^er 
(more  ventrad)  in  position  than  the  pre- 
sutural  macrochasta;    fifth  ventral  abdomi- 
nal sclerite  of  the  male  cleft  beyond  the 
middle,    often    strongly    developed;     body 
color    ver\'    frequently    metallic    green    or 
blue,  or  yellow;    arista  plumose.      (Calli- 

PHORIN.a;) MUSCIDiE  in  part. 

See  page  303  for  generic  synopsis. 
00.  Outermost  posthumeral  macrochaeta  on 
level  or  higher  (more  dorsad)  than  the 
presutural  macrochaeta ;  arista  bare,  pube- 
scent, or  plumose  onh-  on  the  basal  two- 
thirds;,     bod}'    coloring    usually    grayish 

(fig.  106) SARCOPHAGID^a; 

p.  Fifth  ventral  sclerite  of  the  male  either 
wanting  or  with  the  caudal  margin 
straight;      presutural     intraalar     rarely 

present (SARCOPHAGlN.ffi:) 

q.  Fifth  ventral  abdominal  sclerite  of  the 
male  much  reduced,  the  remaining 
segments  with  straight  posterior  mar- 
gin, overlapping  scale-like;  in  the 
female  only  segment  one  and  two  scale- 
like, the  others  wholly  or  in  part 
covered;  stemopleurals  usually  three 
or  more.  Sarcophaga  and  related 
genera. 


302 


HominoxioMs  Arthropods 


qq.  Fifth  ventral  sclerite  of  the  male  plainly 

visible;     sternopleurals   usually    two. 

Sarcophila,  Wohlfahrtia,  Brachycoma, 

Hilarella,       Alillogramma,      Metopia, 

Macronychia,,   Nyctia,    Paramacrony- 

chia,    Pachyphthalmus,    etc. 

pp.  Fifth  ventral   abdominal   sclerite   of   the 

male  deft  to  beyond  the  middle;  ventral 

sclerites     usually     visible,     shield-like. 

Rhinophora,     Phyto,     Melanophora.  .  .  . 

RhINOPHORIN/E 


164.      Glossina  palpalis.      (X4.)      After  Austen. 


Second  ventral  abdominal  sclerite  as  well  as 
the  others  more  or  less  covered,  sometimes 
wholly,  by  the  edges  of  the  dorsal  sclerite. 
.  The    presutural    intraalar   wanting;     ventral 
sclerites  two  to  five  nearly  or  quite  covered 
by  the  edges  of  the  corresponding  dorsal 
sclerites;  base  of  the  antennae  usually  at  or 
below  the  middle  of  the  eye;  arista  usually 
plumose;    legs  usually  elongate;    abdomi- 
nal   segments    with    marginal    and    often 

discal    macrochaetae Dexiid^ 

3.  Presutural  intraalar  present,  if  absent,  then 
the  ventral  sclerites  broadly  exposed 
or    the    fifth    ventral     sclerite  vestigial; 


MuscidcB  303 

base  of  the  antennae  usually  above  the 
middle  of  the  eye;  arista  bare;  at  least 
two  posthumcrals  and  three  posterior 
intraalars  present.  Parasitic  on  cater- 
pillars,   etc Tachinid^ 

SYNOPSIS   OF  THE   PRINCIPAL  GENERA    OF  THE   MUSCID^ff;   OF  THE  WORLD 

a.  Proboscis  long,  directed  forward,  adapted  for  piercing,  or  oral  margin  much 
produced,  snout-like, 
b.  Oral  margin  produced  snout-like;    vibrissa  placed  high  above    the  oral 
margin;  antennal  arista  either  pectinate  or  more  or  less  plumose. 

c.  Antennal    arista    short    or   long-plumose;     neither    sex    with    distinct 
orbital  bristles. 

d.  No  facial  carina  between  the  antenna; Rhynxhomviin^ 

e.  Arista  short-plumose.     R.speciosa.    Europe.  .  .  .Rhynchomyia  R.  D. 
ee.  Arista  long-plumose.  /.  phasina.  Europe  and  Egypt.  Idiopsis.  B.B. 

dd.  With  flattened  carina,  the  bases  of  the  antennee separated;  no  abdom- 
inal macrochastae Cosminik/E 

C.  fuscipennis.     South    Africa Cosmina 

cc.  Antennal  arista  pectinate;    bases  of  the  antenna  separated  by  a  flat- 
tened carina Rhiniin^  R.  D. 

d.  Cell  R5  open,  or  closed  at  the  margin. 

e.  Third  segment  of  the  antenna  twice  as  long  as  the  second;   claws  of 
both  sexes  short;    cell  R5  open.     /.  lunata.     Eastern  Hemisphere. 

Idia  Meigen 

ee.  Third  segment  of  the  antenna  three  times  as  long  as  the  second; 
cell  R5  open  or  closed;  claws  of  the  male  long  and  slender,  of  the 
female  shorter  than  the  last  tarsal  joint.     I.  mandarina,  China. 

Idiella  B.  B. 

dd.  Cell  R5  petiolate Rhinia;  and  Beccarimyia  Rdi. 

bb.  Proboscis  long,  directed  forward,  adapted  for  piercing STOMOXINiE 

c.  Arista  fiat,  pectinate  above  with  plumose  rays;  sternopleurals  1:2; 
bases  of  the  veins  Ri  and  R4+5  without  setae;  base  of  the  media  bowed 
down;   apical  cell  opens  before  the  apex  of  the  wing.     African  species 

:  Glossina    Wied. 

d.  Species  measuring  overtwelve  mm.  in  length.    G.  lottgtpettnis and  fusca. 
dd.  Species  less  than  twelve  mm.  in  length. 
e.  All  segments  of  the  hind  tarsi  black. 

f.  The  fourth  and  ftith  segments  of    the   fore  tarsi  black;    antennae 

black     (fig.     164) G.     palpalis     R.     D. 

ff.  Otherwise  marked G.  hocagei,  tachinoides,  pallicera. 

ee.  First  three  segments  of  the  hind  tarsi  are  yellow,  the  fourth  and 
fifth  segments  are  black, 
f.  Fourth  and  fifth  segments  of  the  first  and  second  pair  of  tarsi  are 
black, 
g.  The  yellow  bands  of  the  abdominal  segments  occupy  a  third  of 

the    segment    (fig.    165) G.    morsitans    Westw. 

gg.  The  yellow  band  on  each  segment  of   the  abdomen  occupies  a 
sixth  of  the  segment G .  longipalpis  Wied. 


304 


Hominoxious  Arthropods 


ff .  Tarsi  of  the  first  and  second  pairs  of  legs  wholly  yellow 

G.  pallidipes  Austen 

:.  Rays  of  the  arista  not  plumose;  only  one  or  two  stemopleurals;  base  of 
the  media  not  strongly  bowed  down;  apical  cell  opens  at  or  very  near 
the  apex  of  the  wing, 
d.  Vein  R4+5  without  setae  at   the  base;    palpi  about  as  long  as  the  pro- 
boscis. 
e.  Arista  pectinate  (i.  e.  rays  on  one  side  only),  the  rays  often  undulate; 
two  yellow  stemopleurals  often  difficult    to   detect;    vein  M  1+2 
only  slightly  bent,  the  apical  cell  hence  wide  open.     The  horn  fly, 
H.  irritans  {  =  Lyperosia  serrata)  and  related  species.     Widely  dis- 
tributed (figs.  167,  168) Hsematobia  R.  D.  not  B.  B. 


165.     Glossina  morsitans.     (x4.)     After  Austen. 


dd 


ee.  Arista  also  with  rays  below;    vein  Mn-2  more    strongly  bent,  the 
apical  cell  hence  less  widely  open. 
Palpi  strongly  spatulate  at  the  tips,   lower  rays  of  the  arista  about 

six  in  number,  B .  sanguinolentus .    South  Asia 

Bdellolarynx    Austen 

Palpi  feebly   spatulate;    apical   cell  of  the  wing  narrowly  open 
slightly  before  the  tip;    stemopleurals  black,  anterior  bristle 

sometimes    absent.     H.    atripalpis.     Europe . 

Haematobosca  Bezzi 

Vein  R4+5  with  setae  at  the  base.* 


f. 


ff. 


*Pachymyia  Macq.  is  closely  related  to  Slomoxys.     It  differs  in  having  the  arista  rayed  both 
above  and  below.     P.  vexans,  Brazil. 


MtiscidcB  305 

e.  Veins  Ri  and  R4-1-5  with  setae  at  the  base;  two  equally  prominent 
sternopleural  macrocha;tae ;  arista  with  rays  both  above  and  be- 
low;   palpi  as  long  as  the  proboscis;   apical  cell  of  the  wing  wide 

open.     L.  tibialis.     {Hccmatobia  B.   B.  not  R.  D.) 

Lyperosiops  Town. 

ee.  Only  vein  R4+5  with    basal  setae;    anterior    sternopleural  macro- 
chajta  wanting;    arista  pectinate, 
f.  Palpi  as  long  as  the  proboscis,  the  latter  stout,  with  fleshy  termi- 
nal labellae;    apical  cell  narrowly  open;    sternopleural  macro- 
chaetag   black.     S.   maculosa   from   Africa  and   related   species 

from  Asia Stygeromyia  Austen 

ff.  Palpi  much  shorter  than  the  proboscis,  the  latter  pointed  at  the 
apex,  without  fleshy  labellae;  apical  cell  of  the  wing  wade  open. 
S.  calcitrans,  the  stable  fly  and  related  species.  Widely  dis- 
tributed in  both  hemispheres  (fig.  no) Stomoxys  Geof. 

aa.  Proboscis  neither  slender  nor  elongate,  the  labellae  flesh}^  and  not  adapted  for 
piercing. 

b.  Hypopleurae  without  a  vertical  row  of    macrochaetae MUSCIN^ 

c.  Arista  bare;   distal  portion  of  R4+5  broadly  curved  at  the  end;    hypop- 
pleurae  with  a  sparse  cluster  of  fine    hairs.     5.  braziliana,  Southern 

States  and  southward Synthesiomyia  B.  B. 

cc.  Arista  pectinate  or  plumose. 

d.  Arista  pectinate.     H.  vittigera,  with  the  posterior  half  of  the  abdomen 

metallic     blue.     Mexico Hemichlora  V.  d.  W. 

dd.  Arista  plumose. 

e.  Middle  tibia  with  one  or  more  prominent  setae  on  the  inner  (flexor) 

surface  beyond  the  middle,  or  inner  surface  very  hairy. 

f.  Ri  ends  distad  of  the  m-cu  crossvein;    R4+5  with  a  broad  curve 

near  its  apical  end.     {  =  Neomesembrina  Sch.na.h\,=Metamesem- 

brina  Tow^n).     M.  meridiana.     Europe.  .  .  .  Mesembrina  Meigen 

ff.  Ri  ends  proximad  of  the  m-cu  crossvein. 

g.  Eyes  pilose,  sometimes  sparsely  in  the  female. 

h.  Female  with  two  or  three  stout  orbital  setae ;  the  hind  metatar- 
sus of  the  male  thickened  below  at  the  base  and  penicillate. 

D.     pratorum.     Europe DasypJwra     R.     D.* 

hh.  Neither  sex  w-ith  orbital  setae. 

i.     Abdomen     without     macrochaetag ;      arista     plumose.     C. 
asiatica.     Eastern    Hemisphere.  .  .    Cryptolucilia    B.    B. 
ii.  Abdomen   with   strong    macrochaetae;     arista   very   short- 
plumose,  nearh'  bare.     B.  tachinina.     Brazil 

Reinwardtia  B.  B. 

gg.  Eyes  bare. 

h.  Body  densely  pilose;    thoracic  macrochaetae  wanting;   middle 

tibiae  much  elongate  and  bent;   last  section  of  R4+5  with  a 

gentle  curve.     H.   {Mesembrina)  mystacea,   et  al.,  Europe 

and    H.    solUaria,    N.    America. ....  Hypodermodes    Tow^n. 

hh.  Body  not  densely  pilose. 

*The  genus  Eudasyphora  Town,  has  recently  been  erected  to  contain  D.  lasiophlhalma. 


3o6 


Hominoxious  Arthropods 


i.  Dorsocentrals  six;  last  section  of  R4+5  with  a  gentle  curve. 

j.  Inner    dorsocentrals    ("acrostichals")    wanting;     sterno- 

pleurals  arranged  1:3.     P.   cyanicolor,  cadaverina,  etc. 

Europe  and  America Pyrellia  R.  D. 

jj.  Inner    dorsocentrals    ("acrostichals")    present;     stemo- 
pleurals  arranged  1:2.     E.  latreillii.     North  America. 

Eumesemhrina   Town. 

ii.  Dorsocentrals  five;  inner  dorsocentrals  present;  last 
section  of  R4+5  with  a  rounded  angle;  stemopleurals 
arranged     1:2.     P.     cornicina     Europe     and   America. 

(Pseudopyrellia  Girsch.) Orthellia  R.  D. 

Middle  tibia  without  a  prominent  bristle  on  the  inner  surface  beyond 
the  middle. 


166.     Pycnosoma  marginale.     (x4.)     After  Graham-Smith. 


f.  Squamula  thoracalis  broadened  mesad  and  caudad  as  far  as  the 
scutellum. 
g.  Stemopleural  macrochfets  arranged  in  an   equilateral  triangle; 
front  of    both    sexes    broad;    gen^e  bare;    dorsocentrals  six, 
small;  wing  not  rilled.     (To  Coenosin^).     Atherigona    Rdi. 
gg.  Stemopleural  macrochaetae  when  three  are  present,  arranged 
in  a  right  triangle, 
h.  Last  section  of  R4-1-5  with  a  more    or  less    rounded  angle 
(fig.  163I). 
i.  Eyes  of  the  male  pilose  or  pubescent,  of  the  female  nearly 
bare;   m-cu  crossvein  usually  at  or  proximad  of  the  mid- 
distance   between   the   r-m   crossvein   and   the   bend   of 

R4_|.5.     P.  ( =  Placomyia  R.  D.)  vitripennis 

Plaxemyia  R.  D. 

ii.  Eyes  bare;   the  m-cu  crossvein  always  nearer  to  the  bend  of 

R4-I-5  than  to  the  r-m  crossvein. 

j.  Apex  of  the  proboscis  when  extended  reveals  a  circlet  of 

stout  chitinous  teeth.     P.  insignis  Austen,  of  India, 

bites  both  man  and  animals.     ( =  Pristirhynchomyia) 

Philaematomyia   Austen 


MuscidcB  307 

jj.  Apex  of  the  proboscis  without  black  teeth. 

k.  Eyes  of  male  separated  by  a  distance  equal  to  a  fourth 

the   width    of    the    head.     House   or    typhoid   fly. 

M.    domestica    L.    Widely   distributed.  .Musca   L. 

kk.  Eyes  of  the  male  contiguous.     E.  corvina.     Europe. 

Eumusca    Town 

hh.  Last  section  of  R4-fo  with  a  gentle  curve  (fig.  102). 
i.  Eyes  pilose. 

j.  Claws  in  the  male  somewhat  elongated;    no  orbitals  in 

either  sex;    antenna;  separated  at  the  base  by  a  flat 

carina;     abdomen    marked    with    red    or   yellow.     G. 

maculata.     Europe  and  America.  .  .  .Graphomyia  R.  D. 

jj.  Claws  short  and  equal  in  the  two  sexes;    two  or  three 

stout  orbital  macrochaetae  in  the  female;    Ri  scarcely 

produced  beyond  the  r-m  crossvein;    eyes  contiguous 

in  the  male.     P.  obsoleta.     Brazil  .  .Phasiophana    Br. 

ii.  Ej'es  bare;    fron to-orbital   macrochaetae  in  a   double  row, 

antennas  contiguous  at  the  base. 

j.  One  or  more  pairs  of  well  developed  anterior  inner  dorso- 

central    (acrostichal)    macrochaetae;     seta   on    extensor 

surface  of  hind  tibia.     M.   assimilis,   stabulans,   etc. 

Europe    and    America Muscina    R.    D. 

jj.  Anterior  inner  dorsocentrals  and  the  setee  on   the  ex- 
tensor surface  of  the  hind  tibia  wanting.     M.  micans, 
etc.      Europe  and  North  America.  .  .  .Morellia  R.  D. 
ff.  Squamula    thoracalis    not    broadened    mesad    and    caudad,    not 
reaching  the  margin  of  the  scutellum;  macrochaetae  on  extensor 
surface  of  the  hind  tibia  wanting. 
g.  Eyes    pubescent.        M.    meditabunda.     Europe   and    America. 

Myiospila  Rdi. 

gg.  Eyes  bare;   Ri  ends  before  the  middle  of  the  wing.     A  number 

of  species  from  the  tropics  of  both  hemispheres 

Clinopera  V.  d.  W. 

bb.  Hypopleurae  with  a  vertical  row  of  macrochaetae. 
c.  Eyes  pubescent. 

d.  Ri  ends  about  opposite  the  r-m  crossvein ;  basal  section  of   R4-1-5  bristly 
nearly  to   the   crossvein;     S.  enigmatica.     Africa.     Somalia   Hough 
dd.  Ri  ends  distad  of  the  r-m  crossvein. 

e.  Eastern     hemisphere.      Australasia.       N.     ochracea,      dasypthalma. 

Neocalliphora  Br. 

ee.  Western  Hemisphere.     T.  musciniim.  Mexico.  .  Tyreomma  V.  d.  W. 
cc.  Eyes  bare. 

d.  The  vibrissal  angle  situated  at  a  noticeable  distance  above  the  level  of 
the  margin  of  the  mouth. 
e.  Sternopleural  macrochaetae  arranged  in  the  order  i  :i. 
f.  Genae  with  microchsetae. 

g.  Body  grayish,  with  depressed  yellow  woolly  hair  among  the 
macrochaetae;  wings  folded  longitudinally  over  the  body  when 


3o8 


Hominoxious  Arthropods 


at  rest.     Cluster  flies.     P.  rudis  and  related  species,  widely 

distributed Pollenia   R.    D.* 

I.  Body  metallic  blue  or  green.     Eastern  Hemisphere, 
h.  Vibrissal  angle  placed  very  high  above  the  oral  margin;    a 
carina  between  the  antenna;    outer  posthumeral  wanting; 

anterior   intraalar   present.     T.   viridaurea.     Java   

ThelychcBta  Br. 


ManrJft 
167.     Horn  fly.      (a)  egg;    (6)  larva;    (c)  puparium;     id)    adult.     (x4).     Bureau  of  Entomolngy 


hh.  Vibrissal  angle  moderately  high  above  the  oral  margin; 
carina  small  or  wanting;  no  post  humeral  macrochasta; 
lower     squamae      hairy      above.      {  =  Paracompsomyia 

Hough)   (fig.   1 66) Pycnosoma  Br. 

ff.  Genae  bare.     5.   terminata.     Eastern  Hemisphere 

Strongyloneura  Bigot 

ee.  Sternopleurals  arranged  2:1. 

f.  Body  metallic  green  or  blue,  with  gray  stripes;   genas  hairy  to  the 
lower  margin ;  post  humerals  often  wanting ;  lower  squamae  bare 

above.     {  =  Compsomyia  Rdi.) Chrysomyia  R.  D. 

g.  With  one  or  two  orbitals;    height  of  bucca  less  than  half  the 

height  of  the  eye.     South  and  east  U.  S.  (fig.  107) 

C  •  marcellaria 

gg.  No  orbitals;  height  of  bucca  about  a  third  less  than  height  of 
eye.     West  U.   S C.  wheeleri  Hough 


*NilelHa,  usually  included  in  this  genus  has  the  apical  cell  petiolate.  A  pollenia  Bezzi,  has 
recently  been  separated  from  Pollenia  to  contain  the  species  P.  nudiuscula.  Both  genera  belong 
to  the  Eastern  hemisphere. 


MuscidcB 


309 


ff.  Body  black  or  sordidly  metallic  greenish  gray,  usually  yellow  pol- 
linose  or  variegate;     genas  at  most  hairy  above.     N.   slygia. 

Eastern  Hemisphere Neopollenia  Br. 

dd.  Vibrissal  angle  situated  nearly  on  a  level  of  the  oral  margin. 
e.  Species  wholly  blackish,  bluish,  or  greenish  metallic  in  color. 

f.  First  section  of  R4+5  with  at  most  three  or  four    small  bristles  at 
the  immediate  base. 
g.  The  bend  of  R4+5  a  gentle  curve;   costal  spine  present;   cell   R^ 
closed,    ending   before   the   apex   of   the   wing.     S.   cuprina. 

Java Synamphoneura  Bigot 

gg.  Bend  of  R4-f  5  angular ;  or  the  insect  diflfers  in  other  characters ; 
dorsal  surface  of  the  squamula  thoracalis  hairy  (except  in 
Melinda);  arista  plumose  only  on  the  basal  two-thirds 
(except  usually  in  Calliphora  and  Eucalliphora) . 


IC8.     Head  of  horn-fly  (.Lyperosia  irritans) ;   (a)  female;  (6)  male;  (c)  lateral  aspect  of  female. 


h 


h.  Arista  plumose  only  on  the  basal  two-thirds. 

i.  Base  of  the  antennae  ventrad  of  the  middle  of  the  eye;  eyes 
of  the  male  nearly  contiguous;  gense  hairy;  second 
abdominal  segment  with  median  marginal  macrochaetae ; 
two,  rarely  three,  postsutural  intraalar  macrochaetae. 
Squamula  thoracalis  dorsally  with  long  black  hairs;  male 
hypopgium  two-segmented,  large,  projecting;  claws 
and  puUvilli  of  the  male  elongate;  three  strong  stemo- 
pleural  macrochastae ;  genae  at  least  half  the  width  of  the 
eye;   buccae  (cheeks)  half  the  height  of  the  eyes;  ovivi- 

parous.     0.    sepulcralis.     Europe Onesia    R.    D. 

Dorsal  surface  of  the  squamula  thoracalis  bare;  male 
hypopygium  small,  scarcely  projecting  below;  claws 
and  pulvilU  not  elongate;  two  stout  stemopleural 
macrochaetae,  sometimes  with  a  delicate  one  below  the 
anterior;  genae  nearly  linear  in  the  male;  buccae  about 
a  third  of  the  eye  height;  oviparous.  M.  ccerulea. 
Europe Melinda.     R.     D. 


JJ- 


3IO 


Hominoxious  Arthropods 


■  ■  Tranjnnse  sulu  r. 


,  .Post  alar  caUus 


/'ropleicra,  ■■ 


front  coxa-  ■ 


^^ .__Mng  bale- 

C7^^^ 

7^ 

P^'r^rr^r-ss^ 

-•           ».,       N 

•r-Tran^vene 
suture 

a.  idc 

p  idc 

a  dc 
,-• • 

....'':^-. ..----- 

■p.h 


a  dc  anttrtcr  dcrjc  centrals 

n  idc  ••    inner    •• 

a.  "  intra  alar 

h  humetO'l-s  ,  • 

p.h  pcjt     " 

\ps  prestdurat 

'  p  dc  pssterior  dcrsc  czfitr&U 

p  idc  •'    inntr    •> 
4ntrao.tar 

pro.  prea/ar=antenpr  jo. 

JO.  Jupra.  aJar 

^     Xs^uajnula   alaru 


.  lOciUftr 


169.     Lateral  and  dorsal  aspects  of  the  thorax,  and  frontal  aspect  of  the  head  of  a  muscoidean 
fly,  with  designations  of  the  parts  commonly  used  in  taxonomic  work. 


MuscidcB 


311 


,  Baso  of  the  antennae  dorsad  of  the  middle  of  the  eye;  eyes 
of   both   sexes   distinctly   separated;     dorsal   surface   of 
the    squamula    thoracalis   with    black   hairs;     two   post 
sutural   intraalar  macrochaeta^. 
j.  Hypop3^gium  of  the  male  large,  with  a  pair  of   slightly 
curved  forceps  whose  ends  are  concealed  in  a  longi- 
tudinal slit  in  the  fifth  ventral  sclerite;   third  posterior 
inner  dorso-central  (acrostichal)  macrochaetse   absent; 
anterior  intraalar  rarely  present;  abdomen  usually  not 
pollinose;  the  second  segment  without  median  marginal 
macrochaetse;    face  yellow.     C.  morliionim,  cadaverina, 
and    related    species.     Both    hemispheres. 
Cynomyia  R.  D.* 


170.    Sepsis  violacea;  puparium  and  adult.    (See  page  297.)    After  Howard. 


jj.  Three  pairs  of  posterior  inner  dorsocentrals  (acrostichals) 

present;    second  abdominal  segment  with  a  row  of 

marginal  macrochaetae ;    genae  hair>',   at  least  above. 

k.  Hypopygium    of   the   male    with    a   projecting    style. 

5.  sty!  if  era.     Europe Sleringomyia  Pok. 


*The  following  three  genera  are  not  sufficiently  well  defined  to  place  in  this  synopsis.  In 
color  and  structural  characters  they  are  closely  related  to  Cynomyia  from  which  they  may  be 
distinguished  as  follows.  Catapicephala  Macq..  represented  by  the  species  C.  splendens  from 
Java,  has  the  sets  on  the  facial  ridges  rising  to  the  base  of  the  antennae  and  has  median  margi- 
nal macrochaetae  on  the  abdominal  segments  two  to  four:  Blepharicnema  Macq.,  represented  by 
B.  splendens  from  Venezuela  has  bare  genae,  oral  setae  not  ascending;  tibiae  villose;  claws  short 
in  both  seiies;  Sarconesia  Bigot  with  the  species  5.  cklorogasler  from  Chile,  setose  genae;  legs 
slender,  not  villose;    claws  of  the  mae!   elongate. 


312  Honiinoxious  Arthropods 

kk.  Hypopygium  of  the  male  without  style.     A.  stelviana 

B.  B Acrophaga  B.  B. 

hh.  Arista  usually  plumose  nearly  to  the  tip;  posterior  dorso- 
centrals  and  inner  dorsocentrals  (acrostichals)  well 
developed;  dorsal  surface  of  the  squamula  thoracalis 
hairy;  abdomen  metallic  and  usually  poUinose;  gense 
hairy, 
i.  With  one  pair  of  ocellar  macrochaetae.  C.  vomitoria, 
erythrocephala,    viridescens,   and  related   species.     Both 

hemispheres Calliphora  R.  D. 

ii.  With  two  strong  pairs  of  ocellar  macrochaetae.  .E.  latifrons. 

Pacific  slope    of    the   U.    S Eucalliphora    Town . 

ff.  First  section  of  R4+5  bristly  near  or  quite  half  way  to  the  small 

crossvein;    dorsal  surface  of  the  squamula  thoracalis  is  bare; 

the  hypopygium  of  the  male  is  inconspicuous. 

g.  Genae  bare;    posterior  inner  and  outer  dorsocentrals  distinct 

and    well    developed.      L.    ccesar,    sericata,     sylvartim,    and 

related    species.     Widely    distributed    in    both    hemispheres 

(fig.  103) Lucilia    R.     D. 

gg.  Genae  with  microchaetae,  at  least  down  to  the  level  of  the  base 
of  the  arista, 
h.  Mesonotum  flattened  behind  the  transverse  suture. 

i.  Posterior  dorsocentrals  inconstant  and  unequally  developed; 
one  pair  of  posterior  inner  dorsocentrals.     P.  terraenovce. 

North    America Protophormia    Town. 

ii.  Posterior  dorsocentrals   well   developed,   the  inner  dorso- 
centrals (acrostichals)  unequally  developed.     P.  azurea, 

chrysorrhcea,  etc.     Europe  and  America 

Protocalliphora   Hough 

hh.  Mesonotum  not  flattened  behind  the  transverse  suture; 
posterior  inner  and  outer  dorsocentrals  inconstant 
and     unequally     developed.     P.     regina.     Europe     and 

America Phormia     R.     D. 

ee.  Species  more  or  less  rufous  or  yellow  in  color. 

f.  Anterior  dorsocentrals  wanting;    first  section  of  the  R4-1-5  at  most 

only  bristly  at  the  base,  bend  near  apex  rectangular,  Ri  ends  over 

the   crossvein;     fronto-orbital   macrochseta   absent;     eyes  of  the 

male  contiguous.     C.  semiviridis.     Mexico .  .  Chloroprocta  V.  d.  W 

ff.  With   another  combination   of  characters. 

g.  Body  robust,  of  large  size,  abdomen  elongate,  not  round;    genas 
with  several  ranges  of  microchaetag ;    vibrissal  ridges  strongly 
convergent;     abdomen    with    well    developed    macrochsetae ; 
costal  spine  usually  absent ;  eyes  of  the  male  widely  separated, 
h.  Peristome  broad,  pteropleural  macrochastae  distinct;    one  or 
two  sternopleurals;    in  the  female  a  single  orbital  macro- 
chasta;     last    abdominal    segment    without    discal    macro- 
chaetae;    hypopygial    processes    of    the    male  with  a   long 
stylet;   second  abdominal  segment  of  the  female  sometimes 


MuscidcB 


313 


314  HominoxioMs  Arthropods 

much  elongate.     A.  luteola   (fig.   86).     Africa.     The  sub- 
genus Choeromyia  Roub.  is  included  here.  Auchmeromyia  B.B. 
hh.     Peristome  narrow;     no  pteropleurals,   two  sternopleurals; 
two  orbitals  in  the  female;    second  segment  not  elongate; 
the  fourth  with  two  well  developed  discal  macrochastae. 

B.   depressa.     Africa Bengalia  R.    D 

gg.  With  another  combination  of  characters. 

h.  Costal  spine  present;  body  in  part  black;  antennae  notice- 
ably shorter  than  the  epistome,  inserted  above  the  middle 
of  the  eye  and  separated  from  each  other  by  a  carina; 
abdominal  segments  with  marginal  macrochaetae;  sterno- 
pleurals 2  :i  or  I  :i Paratricyclea  Villen. 

hh.  Costal  spine  not  distinct,  or  if  present,  insect  otherwise 
different, 
i.  Genae  with  several  ranges  of  microchaetae;  vibrissal  ridges 
strongly  converging;  peristome  broad;  arista  moderately 
plumose;  sternopleurals  usually  i:i;  color  entirely 
testaceous.     C.  anthropophaga   (fig.   87)  and  grunbergi. 

Africa Cordylobia    Griinb. 

ii.  Genae  bare  or  with  but  one  range  of  setae;    vibrissal  ridges 
less  converging;   peristome  narrow;   arista  long  plumose. 
j.  Genae  with  a  single  row  of  microchaetae. 

k.  Sternopleurals  2:1 ;    color  entirely  testaceous 

Ochromyia  Macq.* 

kk.  Sternopleurals  i:i.     P.  varia  Hough.     Africa 

Parochroniyia  Hough 

jj.  Genae  bare. 

k.  Basal  section  of  R4+5  bristly  only  at  the  immediate 
base,  distal  section  with  a  broad  curve;  distal 
portion  of  the  abdomen  metallic;  sternopleurals 
usually  1:1.  rarely  2:1.     M.  ceneiventris  Wd.     Tropic 

America Mesembrinella.  G.  T. 

kk.  R4+5  bristly  at  least  nearly    half  way  to  the  small 
crossvein ;    sternopleurals    i :  i . 

I.  Macrochaetae  of  the  abdomen  marginal;    neither  sex 

with  orbitals;  no  carina  between  the  base  of  the 
antennae;  three  pairs  of  presutural  inner  dorso- 
centrals.  Eastern  hemisphere.  T.  ferruginea. 
Tricyclea  V.  d.  W.  {=  Zonochroa  B.  B.  according 
to  Villeneuve    19 14). 

II.  Abdomen  without  macrochastae;    wing  usually  with 

a    marginal    streak    and    gray    markings.     Brazil 
Hemilucilia  B.   B. 


*Plinlhomyia  Rdi.  and  Hemigymnochala  Corti  are  related  to  Ochromyia,  though  too  briefly 
described  to  place  in  the  key. 


Muscoidea 


315 


J 


k 


P 


^'^ 


Left  hand  stigmata  of  the  larvae  of  muscoidea.  Third  instar.  (a)  LuciUa  caesar; 
(i>)  Calliphora  vomitoria;  (c)  Stomoxys  calcitrans;  (d)  Pseudopyiellia  cornicina; 
(e)  Pyrellia  cadavarina;  (/)  Lyperosia  irritans;  (g)  Mesembrina  mystacea;  Qi) 
Mesembrina  meridiana;  d)  Myospila  meditabunda;  (i)  Mydaea  umbana;  {k) 
PoHetes  alboHneata;  (i)  Foliates  lardaria;  (in)  Morellia  hortorum;  (n)  Hydrotaea 
dentipes;  (o)  Hebecnema  umbratica;  (-p)  H.  vespertina;  (5)  Limnophora  sep- 
temnotata;  (r)  Muscina  stabulans.  (a  and6)  after  MacGregor;  {d\  after  Banks; 
all  others  after  Portchinsky.  Magnification  varies.  The  relative  distance  to  the 
median  line  is  indicated  in  each  figure. 


3i6  Hominoxious  Arthropods 

SIPHONAPTERA.     Fleas 
Adapted  from  a  table  published  by  Oudemans. 
a.  Elongated  fleas,  with  jointed   (articulated)  head,  with  combs   (ctenidia)   on 
head  and  thorax;    with  long,  oval,  free-jointed  flagellum  of  the  antenna 

(fig.    92d) Suborder    FRACTICIPATA 

b.  With  ctenidia  in  front  of  the  antennae  and  on  the  genae  (cheeks);    maxillae 
with  acute  apices;   labial  palpi  five-segmented,  symmetrical;   eyes  poorly 

developed  or  wanting.     On  rodents Hystrichopsyllid^ 

c.  Abdominal  segments  without  ctenidia. 

d.  Post-tibial  spines  in  pairs  and  not  in  a  very  close  set  row;  head  with 

ctenidia Ctenophthalmus     Kol. 

dd.  Post-tibial  spines  mostly  single  and  in  a  close  set  row.     Ctenopsyllus 

and  Leptopsyllus.     The  last  genus  has  recently  been  erected  for 

L.  musculi,  a  widely  distributed  species  occurring  on  rats  and  mice. 

cc.  Abdominal  segments  with  one  or  more  ctenidia;    post-tibial  spines  in 

numerous,  short,  close-set  transverse  rows  on  posterior  border  with 

about  four  spines  in  each  row.  H.  americana .  .  Hystrichopsylla  Taschenb. 

bb.  With  only  two  pairs  of  subfrontal  ctenidia;    labial  palpi  five-segmented, 

symmetrical;     eyes   vestigial   or   wanting.     On   bats.      (  =  Ischnops\x- 

LiD^) Nycteridips\xlid.« 

With  more  or  less  blunt  maxilla;  all  tibiae  with  notch;  a  single  antepygi- 
dial  bristle;  metepimeron  without  ctenidium.  N.  crosbyi  from 
Missouri  was  found  on  bats.  Rothschild  suggests  that  this  is  probably 
the  same  as  N.  insignis. 

{  =  Ischnopsyllus  =  Ceratopsyllus),     Nyderidiphilus 

aa.  Head  not  jointed,  i.e.  the  segments  coalescent,  traces  of  the  segmentation 
still  being  visible  in  the  presence  of  the  vertex  tubercle,  the  falx  (sickle- 
shaped  process),  and  a  suture Suborder  INTEGRICIPITA 

b.  Flagellum  of  the  antennae  long  and  oval. 

c.  Usually  elongate  fleas,  with  a  free-segmented  flagellum  of  the  antenna; 

thorax  not  shorter  than  the  head,  longer  than  the  first  tergite. 

d.  Genas  of  the  head  and  the  pronotum  with  ctenidia ....  Neopsyllid^ 

e.  Labial  palpi  four  or  five-segmented;    symmetrical;    hind  coxae  with 

patch  of  spines  inside;   row  of  six  spatulate  spines  on  each  side  in 

front   of   the   antennae.      C.    ornata  found   on   a   California   mole 

Corypsylla 

ee.  Labial     palpi      two-segmented,      transparent,     membranous.      On 

hares Spilopsyllus  Baker 

dd.  No  ctenidium  on  the  head. 

e.  Pronotum  with  ctenidium DOLICHOPSYLLID.* 

f.  Labial  palpi  five-segmented,  symmetrical. 

g.  Antepygidial  bristles  one  to  three;   eyes  present. 

h.  Inner  side  of  hind  coxae  distally  with  a  comb  of  minute  teeth ; 

falx  present.     On  rodents  and  carnivores 

Odontopsyllus  Baker 

hh.  Inner  side  of  hind  coxae  without  comb  or  teeth.     Many 

North  American  species  on  rodents 

Ceratophyllus   Curtis 


Siphonaptera  317 

gg.  Antepygidial  bristles   five  on   each   side;    eyes  absent;  suture 

white.     D.  stylosus  on  rodents Dolichopsyllus  Baker 

ff.   Labial  palpi  four  or  five-segmented;    asymmetrical  (membranous 
behind),  apex  acute.     Iloplopsyllus  anomalus  found  on  Spermo- 

philes  in  Colorado Hoplopsyllid^ 

ee.  Pronotum     without    ctenidium.     Anomiopsyllus    califoriiicus    and 

iiudatus  on  rodents Anomiopsyllid/E 

CO.  Very  short  fleas;  flagellum  of  the  antenna  with  pseudo-segments  coales- 
cent;    thorax  much  shorter  than  the  head  and  than  the  first  tergite 

HECTOPSYLLID.ffi; 

Flagellum  of  the  antenna  with  six  coalescent  pseudo-segments ;  maxilla 

blunt.     The  chigger  on  man  (fig.  93).  D.  penetrans 

( =Rhynchoprion  =  Sarcopsylla)  Dermatophilus  Guc^rin 

bb.  Flagellum  short,  round,  free  portion  of  the  first  segment  shaped  like  a 
mandolin. 
c.  Thorax  not  shorter  than  the  head,  longer  than  the  first  tergite;   flagellum 
either  with  free  segments  or  in  part  with  the  segments  coalescent. 
d.  Head  and  pronotum  with  ctenidium;    laljial  palpi  asymmetrical.  .  .  . 

ARCIL«OPSYLLID.ffi; 

With  four  subfrontal,  four  genal,  and  one  angular  ctenidia.     Widely 

distributed Ctenocephalus  Kol. 

e.  Head  rounded  in  front  (fig.  92a).     Dog  flea C.  canis 

ee.  Head  long  and  flat  (fig.  92b).     Cat  flea C.  fells 

dd.  Neither  head   nor  pronotum   with   ctenidium.     Labial   palpi   asym- 
metrical, membranous  behind PULICID.® 

e.  Mesosternite  narrow,  without  internal  rod-like  thickening  from  the 

insertion  of  the  coxae  upwards.     Human  flea,  etc Pulex  L. 

ee.  Mesosternite  broad  with  a  rod-like  internal  thickening  from  the 
insertionof  the  coxae  upwards  (fig.  89).     X.  (Loemopsylla)  cheopis, 

plague  or  rat  flea Xenopsylla 

cc.  Thorax  much  shorter  than  the  head  and  than  the  first  tergite.  Echi- 
dnophagidae.  E.  gallinacea,  the  hen  flea  also  attacks  man  (fig.  96). 
( =  Argopsylla  =Xestopsylla)  Echidnophaga  011iff_ 


APPENDIX 
HYDROCYANIC  ACID  GAS  AGAINST  HOUSEHOLD  INSECTS 

The  following  directions  for  fumigating  with  hydrocyanic  acid 
gas  are  taken  from  Professor  Herrick's  circular  published  by  the 
Cornell  Reading  Course: 

Hydrocyanic  acid  gas  has  been  used  successfully  against  house- 
hold insects  and  will  probably  be  used  more  and  more  in  the  future. 
It  is  particularly  effective  against  bed-bugs,  and  cockroaches,  but 
because  it  is  such  a  deadly  poison  it  must  he  used  very  carefully. 

The  gas  is  generated  from  the  salt  potassium  cyanid,  by  treating 
it  with  sulfuric  acid  diluted  with  water.  Potassium  cyanid  is  a 
most  poisonous  substance  and  the  gas  emanating  from  it  is  also 
deadly  to  most,  if  not  all,  forms  of  animal  life.  The  greatest  care 
must  always  be  exercised  in  fumigating  houses  or  rooms  in  buildings 
that  are  occupied.  Before  fumigation  a  house  should  be  vacated. 
It  is  not  necessary  to  move  furniture  or  belongings  except  brass  or 
nickel  objects,  which  may  be  somewhat  tarnished,  and  butter,  milk, 
and  other  larder  supplies  that  are  likely  to  absorb  gas.  If  the  nickel 
and  brass  fixtures  or  objects  are  carefully  covered  with  blankets 
they  will  usually  be  sufficiently  protected. 

There  may  be  danger  in  fumigating  one  house  in  a  solid  row  of 
houses  if  there  is  a  crack  in  the  walls  through  which  the  gas  may  find 
its  way.  It  also  follows  that  the  fumigation  of  one  room  in  a  house 
may  endanger  the  occupants  of  an  adjoining  room  if  the  walls  be- 
tween the  two  rooms  are  not  perfectly  tight.  It  is  necessary  to  keep 
all  these  points  in  mind  and  to  do  the  work  deliberately  and  thought- 
fully. The  writer  has  fumigated  a  large  college  dormitory  of  253 
rooms,  once  a  year  for  several  years,  without  the  slightest  accident 
of  any  kind.  In  order  to  fumigate  this  building  about  340  pounds 
of  cyanid  and  the  same  amount  of  sulfuric  acid  were  used  each  time. 
In  addition  to  this,  the  writer  has  fumigated  single  rooms  and  smaller 
houses  with  the  gas.  In  one  instance  the  generating  jars  were  too 
small;  the  liquid  boiled  over  and  injured  the  floors  and  the  rugs. 
Such  an  accident  should  be  avoided  by  the  use  of  large  jars  and  by 
placing  old  rugs  or  a  quantity  of  newspapers  beneath  the  jars. 


318 


The  Proportions  of  Ingredients  319 

The  Proportions  of  Ingredients 

Experiments  and  experience  have  shown  that  the  potassium 
cyanid  should  be  ninety-eight  per  cent  pure  in  order  to  give  satis- 
factory results.  The  purchaser  should  insist  on  the  cyanid  being  of 
at  least  that  purity,  and  it  should  be  procurable  at  not  more  than 
forty  cents  per  pound.  The  crude  form  of  sulfuric  acid  may  be  used. 
It  is  a  thickish,  brown  liquid  and  should  not  cost  more  than  four  or 
five  cents  a  poimd.  If  a  room  is  made  tight,  one  ounce  of  cyanid  for 
every  one  hundred  cubic  feet  of  space  has  been  shown  to  be  sufficient. 
It  is  combined  wdth  the  acid  and  water  in  the  following  proportions : 

Potassium  cyanid i  ounce 

Commercial  sulfuric  acid i  fluid  ounce 

Water 3  fluid  ounces 

A  Single  Room   as  an   Example 

Suppose  a  room  to  be  12  by  15  by  8  feet.  It  will  contain 
I2X  15x8,  or  1440  cubic  feet.  For  convenience  the  writer  always 
works  on  the  basis  of  complete  hundreds;  in  this  case  he  would 
work  on  the  basis  of  1500  cubic  feet,  and  thus  be  sure  to  have  enough. 
The  foregoing  room,  then,  would  require  15  ounces  of  cyanid,  15 
ounces  of  sulfuric  acid,  and  45  ounces  of  water.  The  room  should 
be  made  as  tight  as  possible  by  stopping  all  the  larger  openings, 
such  as  fireplaces  and  chimney  flues,  with  old  rags  or  blankets. 
Cracks  about  windows  or  in  other  places  should  be  sealed  with  narrow 
strips  of  newspaper  weU  soaked  in  water.  Strips  of  newspaper  two 
or  three  inches  wide  that  have  been  thoroughly  soaked  in  water  may 
be  applied  quickly  and  effectively  over  the  cracks  around  the  window 
sash  and  elsewhere.  Such  strips  will  stick  closely  for  several  hours 
and  may  be  easily  removed  at  the  conclusion  of  the  work. 

While  the  room  is  being  made  tight,  the  ingredients  should  be 
measured  according  to  the  formula  already  given.  The  water  should 
be  measured  and  poured  first  into  a  stone  jar  for  holding  at  least  two 
gallons.  The  jar  should  be  placed  in  the  middle  of  the  room,  with 
an  old  rug  or  several  newspapers  under  it  in  order  to  protect  the  floor. 

The  required  amount  of  sulfuric  acid  should  then  be  poured 
rather  slowly  into  the  water.  This  process  must  never  be  reversed; 
that  is,  the  acid  must  never  be  poured  into  the  jar  first.  The  cya.m6. 
should  be  weighed  and  put  into  a  paper  bag  beside  the  jar.  All  hats, 
coats,  or  other  articles  that  will  be  needed  before  the  work  is  over 


320  Hydrocyanic  Acid  Gas  Against  Household  Insects 

should  be  removed  from  the  room.  When  everything  is  ready  the 
operator  should  drop  the  bag  of  cyamd  gently  into  the  jar,  holding 
his  breath,  and  should  walk  quickly  out  of  the  room.  The  steam- 
like gas  does  not  rise  immediately  under  these  conditions,  and  ample 
time  is  given  for  the  operator  to  walk  out  and  shut  the  door.  If 
preferred,  however,  the  paper  bag  may  be  suspended  by  a  string 
passing  through  a  screw  eye  in  the  ceiling  and  then  through  the  key- 
hole of  the  door.  In  this  case  the  bag  may  be  lowered  from  the  out- 
side after  the  operator  has  left  the  room  and  closed  the  door. 

The  writer  has  most  often  started  the  fumigation  toward  evening 
and  left  it  going  all  night,  opening  the  doors  in  the  morning.  The 
work  can  be  done,  however,  at  any  time  during  the  day  and  should 
extend  over  a  period  of  five  or  six  hours  at  least.  It  is  said  that  bet- 
ter results  will  be  obtained  in  a  temperature  of  70°  F.,  or  above,  than 
at  a  lower  degree. 

At  the  close  of  the  operation  the  windows  and  doors  may  be  opened 
from  the  outside.  In  the  course  of  two  or  three  hours  the  gas  should 
be  dissipated  enough  to  allow  a  person  to  enter  the  room  without 
danger.  The  odor  of  the  gas  is  like  that  of  peach  kernels  and  is  easily 
recognized.  The  room  should  not  be  occupied  until  the  odor  has 
disappeared. 

Fumigating  a  Large  House 

The  fumigation  of  a  large  house  is  merely  a  repetition,  in  each  room 
and  hall,  of  the  operations  already  described  for  a  single  room.  All 
the  rooms  should  be  made  tight,  and  the  proper  quantities  of  water 
and  sulfuric  acid  should  be  measured  and  poured  into  jars  placed 
in  each  room  with  the  cyanid  in  bags  besides  the  jars.  When  all 
is  ready,  the  operator  should  go  to  the  top  floor  and  work  downward 
because  the  gas  is  lighter  than  air  and  tends  to  rise. 

Precautions 

The  cyanid  should  be  broken  up  into  small  pieces  not  larger  than 
small  eggs.  This  can  best  be  done  on  a  cement  or  brick  pavement. 
It  would  be  advantageous  to  wear  gloves  in  order  to  protect  the  hands, 
although  the  writer  has  broken  many  pounds  of  cyanid  without  any 
protection  on  the  hands.  Wash  the  hands  thoroughly  at  frequent 
intervals  in  order  to  remove  the  cyanid. 

The  operations  ot  the  work  must  be  carried  out  according  to 
directions. 


Precautions  321 

The  work  should  be  done  by  a  calm,  thoughtful  and  careful 
person— best  by  one  who  has  had  some  experience. 

Conspicuous  notices  of  what  has  been  done  should  be  placed  on 
the  doors,  and  the  doors  should  be  locked  so  that  no  one  can  stray 
into  the  rooms. 

The  gas  is  lighter  than  air,  therefore  one  should  always  begin  in  the 
rooms  at  the  top  of  the  house  and  work  down. 

After  fumigation  is  over  the  contents  of  the  jar  should  be  emptied 
into  the  sewer  or  some  other  safe  place.  The  jars  should  be  washed 
thoroughly  before  they  are  used  again. 

It  must  be  remembered  that  cyanid  is  a  deadly  poison;  but  it  is 
very  efficient  against  household  insects,  if  carefully  used,  and  is  not 
particularly  dangerous  when  properly  handled. 

LESIONS  PRODUCED  BY  THE  BITE  OF  THE  BLACK-FLY 

While  this  text  was  in  press  there  came  to  hand  an  important  paper 
presenting  a  phase  of  the  subject  of  black  fly  injury  so  different  from 
others  heretofore  given  that  we  deem  it  expedient  to  reproduce  here 
the  author's  summary.  The  paper  was  published  in  The  Journal 
of  Cutaneous  Diseases,  for  November  and  December,  19 14,  under  the 
title  of  "A  Clinical,  Pathological  and  Experimental  Study  of  the 
Lesions  Produced  by  the  Bite  of  the  Black  Fly"  {SimuUum  venus- 
tum),"  by  Dr.  John  Hinchman  Stokes,  of  the  University  of  Michigan. 

Resume  and  Discussion  of  Experimental  Findings 

The  principal  positive  result  of  the  work  has  been  the  experimental 
reproduction  of  the  lesion  produced  by  the  black-fly  in  characteristic 
histological  detail  by  the  use  of  preserved  flies.  The  experimental 
lesions  not  only  reproduced  the  pathological  pictures,  but  followed 
a  clinical  course,  which  in  local  symptomatology^  especially,  tallied 
closely  with  that  of  the  bite.  This  the  writer  interprets  as  satis- 
factory evidence  that  the  lesion  is  not  produced  by  any  living  infec- 
tive agent.  The  experiments  performed  do  not  identify  the  nature 
of  the  toxic  agent.  Tentatively  they  seem  to  bring  out,  however, 
the  following  characteristics. 

1.  The  product  of  alcoholic  extraction  of  flies  do  not  contain 
the  toxic  agent. 

2.  The  toxic  agent  is  not  inactivated  by  alcohol. 

3.  The  toxic  agent  is  not  destroyed  by  dr^^ing  fixed  flies. 

4.  The  toxic  agent  is  not  affected  by  glycerin,  but  is,  if  anything, 
more  active  in  pastes  made  from  the  ground  fly  and  glycerin,  than 
in  the  ground  flies  as  such. 


322  Lesions  Produced  by  the  Bite  of  the  Black-fly 

5.  The  toxic  agent  is  rendered  inactive  or  destroyed  by  hydro- 
chloric acid  in  a  concentration  of  0.25%. 

6.  The  toxic  agent  is  most  abundant  in  the  region  of  the  ana- 
tomical structures  connected  with  the  biting  and  salivary  apparatus 
(head  and  thorax). 

7.  The  toxic  agent  is  not  affected  by  a  0.5  %  solution  of  sodium 
bicarbonate. 

8.  The  toxic  agent  is  not  affected  by  exposure  to  dry  heat  at 
100°  C.  for  two  hours. 

9.  The  toxic  agent  is  destroyed  or  rendered  inactive  in  alkaline 
solution  by  a  typical  hydrolytic  ferment,  pancreatin. 

10.  Incomplete  experimental  evidence  suggests  that  the  activity 
of  the  toxic  agent  may  be  heightened  by  a  possible  lytic  action  of 
the  blood  serum  of  a  sensitive  individual,  and  that  the  sensitive  serum 
itself  may  contain  the  toxic  agent  in  solution. 

These  results,  as  far  as  they  go  (omitting  No.  10),  accord  with 
Langer's  except  on  the  point  of  alcoholic  solubility  and  the  effect 
of  acids.  The  actual  nature  of  the  toxic  agent  in  the  black-fly  is 
left  a  matter  of  speculation. 

The  following  working  theories  have  suggested  themselves  to 
the  writer.  First,  the  toxin  may  be,  as  Langer  believes  in  the  case 
of  the  bee,  an  alkaloidal  base,  toxic  as  such,  and  neutralized  after 
injection  by  antibodies  produced  for  the  occasion  by  the  body.  In 
such  a  case  the  view  that  a  partial  local  fixation  of  the  toxin  occurs, 
which  prevents  its  immediate  diffusion,  is  acceptable.  Through 
chemotactic  action,  special  cells  capable  of  breaking  up  the  toxin 
into  harmless  elements  are  attracted  to  the  scene.  Their  function 
may  be,  on  the  other  hand,  to  neutrahze  directly,  not  by  lysis. 
This  would  explain  the  role  of  the  eosinophiles  in  the  black-fly  lesion. 
If  their  activities  be  essential  to  the  destruction  or  neutralization 
of  the  toxin,  one  would  expect  them  to  be  most  numerous  where 
there  was  least  reaction.  This  would  be  at  the  site  of  a  bite  in  an 
immune  individual.  A  point  of  special  interest  for  further  investiga- 
tion, would  be  the  study  of  such  a  lesion. 

Second,  it  is  conceivable  that  the  injected  saliva  of  the  fly  does 
not  contain  an  agent  toxic  as  such.  It  is  possible,  that  Hke  many 
foreign  proteins,  it  only  becomes  toxic  when  broken  down.  The 
completeness  and  rapidity  of  the  breaking  down  depends  on  the 
number  of  eosinophiles  present.  In  such  a  case  immunity  should 
again  be  marked  by  intense  eosinophilia. 


Lesions  Produced  by  the  Bite  of  the  Black-fly 


323 


si 

5? 


324  Lesions  Produced  by  the  Bite  of  the  Black-fly 

Third,  lytic  agents  in  the  blood  serum  may  play  the  chief  role 
in  the  liberation  of  the  toxic  agent  from  its  non-toxic  combination. 
An  immune  individual  would  then  be  one  whose  immunity  was  not 
the  positive  one  of  antibody  formation,  but  the  negative  immunity 
of  failure  to  metabolize.  An  immune  lesion  in  such  a  case  might 
be  conceived  as  presenting  no  eosinophilia,  since  no  toxin  is  liberated. 
If  the  liberation  of  the  toxin  is  dependent  upon  lytic  agents  present 
in  the  serum  rather  than  in  any  cellular  elements,  a  rational  explana- 
tion would  be  available  for  the  apparent  results  (subject  to  con- 
firmation) of  the  experiment  with  sensitive  and  immune  sera.  In 
this  experiment  it  will  be  recalled  that  the  sensitive  serum  seemed  to 
bring  out  the  toxicity  of  the  ground  flies,  and  the  serum  itself  seemed 
even  to  contain  some  of  the  dissolved  or  liberated  toxin.  The 
slowness  with  which  a  lesion  develops  in  the  case  of  the  black-fly 
bite  supports  the  view  of  the  initial  lack  of  toxicity  of  the  injected 
material.  The  entire  absence  of  early  subjective  symptoms,  such 
as  pain,  burning,  etc.,  is  further  evidence  for  this  view.  It  would 
appear  as  if  no  reaction  occurred  until  lysis  of  an  originally  non- 
toxic substance  had  begun.  Regarding  the  toxin  itself  as  the  chemo- 
tactic  agent  which  attracts  eosinophiles,  its  liberation  in  the  lytic 
process  and  diffusion  through  the  blood  stream  attracts  the  cells 
in  question  to  the  point  at  which  it  is  being  Hberated.  Arriving 
upon  the  scene,  these  cells  assist  in  its  neutralization. 

The  last  view  presented  is  the  one  to  which  the  author  inclines 
as  the  one  which  most  adequately  explains  the  phenomena. 

A  fourth  view  is  that  the  initial  injection  of  a  foreign  protein  by 
the  fly  (i.e.,  with  the  flrst  bite)  sensitizes  the  body  to  that  protein. 
Its  subsequent  injection  at  any  point  in  the  skin  gives  rise  to  a 
local  expression  of  systematic  sensitization.  Such  local  sensitization 
reactions  have  been  described  by  Arthus  and  Breton,  by  Ham- 
burger and  Pollack  and  by  Cowie.  The  description  of  such  a  lesion 
given  by  the  first  named  authors,  in  the  rabbit,  however,  does  not 
suggest,  histopathologically  at  least,  a  strong  resemblance  to  that 
of  the  black-fly.  Such  an  explanation  of  many  insect  urticarias 
deserves  further  investigation,  however,  and  may  align  them  under 
cutaneous  expressions  of  anaphylaxis  to  a  foreign  protein  injected 
by  the  insect.  Depending  on  the  chemical  nature  of  the  protein 
injected,  a  specific  chemotactic  reaction  like  eosinophilia  may  or 
may  not  occur.  Viewed  in  this  light  the  development  of  immunity 
to  insect  bites  assumes  a  place  in  the  larger  problem  of  anaphylaxis. 


Lesions  Produced  by  the  Bite  of  the  Black-fly 


325 


174. 


Experimental  lesion  produced  from  alcohol-fixed  flies,  dried  and  ground  into  a 
paste  with  glycerin. 


326  Lesions  Produced  by  the  Bite  of  the  Black-fly 

Summary 

In  order  to  bring  the  results  of  the  foregoing  studies  together, 
the  author  appends  the  following  resume  of  the  clinical  data  pre- 
sented in  the  first  paper. 

The  black -fly,  Simulium  venustum,  inflicts  a  painless  bite,  with 
ecchymosis  and  haemorrhage  at  the  site  of  puncture.  A  papulo- 
vesicular lesion  upon  an  urticarial  base  slowly  develops,  the  full 
course  of  the  lesion  occupying  several  days  to  several  weeks.  Marked 
differences  in  individual  reaction  occur,  but  the  typical  course  in- 
volves four  stages.  These  are,  in  chronological  order,  the  papular 
stage,  the  vesicular  or  pseudovesicular,  the  mature  vesico-papular  or 
weeping  papular  stage  and  the  stage  of  involution  terminating  in  a 
scar.  The  papule  develops  in  from  3  to  24  hours.  The  early  pseudo- 
vesicle  develops  in  24  to  48  hours.  The  mature  vesico-papular  lesion 
develops  by  the  third  to  fifth  day  and  may  last  from  a  few  days  to 
three  weeks.  Involution  is  marked  by  cessation  of  oozing,  subsidence 
of  the  papule  and  scar-like  changes  at  the  site  of  the  lesion.  The 
symptoms  accompanying  this  cycle  consist  of  severe  localized  or 
diffused  pruritus,  with  some  heat  and  burning  in  the  earlier  stages 
if  the  oedema  is  marked.  The  pruritus  appears  with  the  pseudo- 
vesicular  stage  and  exhibits  extraordinary  persistence  and  a  marked 
tendency  to  periodic  spontaneous  exacerbation.  The  flies  tend  to 
group  their  bites  and  confluence  of  the  developing  lesions  in  such 
cases  may  result  in  extensive  oedema  with  the  formation  of  oozing 
and  crusted  plaques.  A  special  tendency  on  the  part  of  the  flies 
to  attack  the  skin  about  the  cheeks,  eyes  and  the  neck  along  the 
hair  line  and  behind  the  ears,  is  noted.  In  these  sites  inflammation 
and  oedema  may  be  extreme. 

A  distinctive  satellite  adeonpathy  of  the  cervical  glands  develops 
in  the  majority  of  susceptible  persons  within  48  hours  after  being 
bitten  in  the  typical  sites.  This  adenopathy  is  marked,  discrete 
and  painful,  the  glands  often  exquisitely  tender  on  pressure.  It 
subsides  without  suppuration. 

Immunity  may  be  developed  to  all  except  the  earliest  manifesta- 
tions, by  repeated  exposures.  Such  an  immunity  in  natives  of  an 
infested  locality  is  usually  highly  developed.  There  are  also  ap- 
parently seasonal  variations  in  the  virulence  of  the  fly  and  variations 
in  the  reaction  of  the  same  individual  to  different  bites. 

Constitutional  effects  were  not  observed  but  have  been  reported. 


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Whitfield,    A.     1912.     A    method    of    rapidly    exterminating    pediculi    capitis. 

Lancet  1912  (2),  p.  1648.     See  notes. 
Williston,  S.  W.     1908.     Manual  of  the  North  American  Diptera,  New  Haven, 

p.  1-405. 
Wilson,  G.  B.  and  Chowning,  W.  M.     1903.     Studies  m  Piropl  ismosis  hominis. 

Journ.  Inf.  Dis.,  iv,  p.  31-57. 
Wilson,   W.   H.     1904.     On   the   venom  of   scorpions.     Rec.   Egyptian   Gov't 

School  of  Medicine,  Cairo,  ii,  p.  7-44. 


INDEX 


Abscess    178 

Acanthia    87 

Acariasis    58 

Acarina 23,  58,  131,  259 

Acarus  dj-senteriae 132 

Accidental  parasites 131,  132,  134 

Aedes 194,    293 

Aedes  calopus .  .  .  182,  201,  205,  206,  208 

Aedes  cantator loi 

Aedes  sollicitans loi 

Aedes  toeniorhynchus loi 

Aerobic   bacteria 152 

Aestivo-autumnal 186 

African  Relapsing  Fever 230 

Akis  spinosa 177 

Alternation  of  Generations 175 

Amblyomma 264 

Amblyomma  americanum 67 

Amblyomma  cajennense 67 

American  dog  tick 228 

Amoeboid  organism 1 89 

Anisolabis  annulipes   177 

Anterior  poliomyelitis 241 

Anopheles 194,    291 

Anopheles  crucians 199 

Anopheles  maculipennis 182 

Anopheles  punctipennis 198 

Anopheles  quadrimaculatus 197 

Anopheline    192 

Anthocoris 279 

Anthomyiidae    300 

Anthomyia    138 

Anthrax 165 

Antipruritic  treatment 72 

Ants  42 

Aphiochaeta 295 

Apis  mellifica 36 

Arachnida 258 

Araneida    6 

Argas 64 

Argas  persicus 63,  235,  237 

Argasidae 62 

Argopsylla 317 

Argus  259 

341 


Arilus 284 

Arthopods,  poisonous 6 

Asopia  farinalis 177 

Assassin-bugs 31,  219 

Auchmeromyia 117 

Automeris  io 47 

Avicularoidea 12 

Babesia    226 

Babesia  bovis 223 

Babesia  ovis 225 

Babesiosis   221-222 

Bacilli 170 

Bacillus  icteroides 202,  205 

Bacillus  pestis 166 

Bacillus   typhosus 153 

Back  swimmers 30 

Bdellolarynx 304 

Beauperthuy,  Louis  Daniel 2 

Bed-bug 86,  88,  90,  173,  219-220 

Bed-bug,  cone-nosed 92 

Blister   beetles 54 

Belostoma 28,    277 

Belostoma  americana 31 

Belostomatidas    30 

Bengalia 314 

Bird-spiders 10 

Black  death i,  166 

Black  flies 33,  104,  247 

Black  heads 80 

Blaps  mortisaga 134 

Blepharoceridae 286 

Boophilus    264 

Boophilus  annulatus 67,  223-225 

Bot-flies 112 

Blue  bottle  flies 140 

Brill's  disease 238 

Brown-tailed  moth 48 

Bruck 34 

Buthus  quinquestriatus 21 

Cabbage  butterfly 56 

Calliphora 136,  140,  312 

Calliphora  erythrocephala 141 


342 


Index 


Calobata    296 

Camponotinse  43 

Cancer  254 

Cantharidin 54 

Cantharidin  poison 55 

Canthariasis    134 

Capsidae 280 

Carriers,  simple 4,  144 

Carriers  of  disease 144 

Carrion's  fever 253 

Caterpillar  rash 45 

Cat  flea • 172 

Cattle  ticks 222 

Causative  organism 170 

Cellia 291 

Centipedes 25,  257 

Ceratophyllus 120,   316 

Ceratophyllus  acutus 123 

Ceratophyllus  fasciatus.  .122,  172,  213 

Ceratopogon 108 

Cheese-fly    i37 

Cheyletus  eruditus 271 

Chigger    60,  70 

Chigoes    126 

Chilopoda 25,  257 

Chiracanthium  nutrix 18 

Chironomidag    107 

Chorioptes 270 

Chrysomelid 55 

Chrysomyia 136,  308 

Chrysomyia  macellaria 1 17,  140 

Chrysops  294 

Chylous  dropsy 1 79 

Chyluria    178 

Cicadidse 55 

Cimex  L 278 

Cimex  boueti 92 

Cimex  columbarius 92 

Cimex  hemipterus 91,  220 

Cimex  hirundinis 92 

Cimex  inodorus 92 

Cimex  lectularius 87,  219 

Citheronia  regalis 44 

Clinocoris    87 

Coleoptera 134,  274 

Comedons 80 

Complete  metamorphosis 80 

Compressor  muscle 20 


Compsomyia 117 

Cone-nosed  bed-bug 92 

Conjunctivitis,    nodular 52 

Conorhinus 282 

Conorhinus  megistus 93,  219-220 

Conorhinus  rubrofasciatus 220 

Conorhinus  sanguisugus 32,  92 

Copra  itch 72 

Cordylobia    118 

Coriscus 280 

Coriscus  subcoleoptratus 32 

Creeping  myasis 112 

Crustacea 257 

Cryptocystis  176 

Cryptotoxic 54-55 

Cteniza  sauvagei 13 

Ctenocephalus 120,  172,  213,  317 

Culex 194,  201,  293 

Culex  pipiens 35,  98 

Culex  quinquefasciatus 180 

Culex  soUicitans 200 

Culex  territans loi 

CuHcidse 33,  97 

Culicin 34 

Culicoides 109,  288 

Cyclops 183,257 

Cynomyia 136,  311 

Dance,  St.  Vitus 8 

Dancing  mania 8 

Deer-flies no 

Definitive  host 192 

Demodecidae  78 

Demodex 259 

Demodex   foUiculorum 78 

Dermacentor 262 

Dermacentor  andersoni 67,  228 

Dermacentor  occidentalis 227 

Dermacentor  variabilis 67 

Dermacentor  venustus 24,  228 

Dermanyssidae    68 

Dermanyssus    266 

Dermanyssus  gallinae 68 

Dermatitis 72,  77.  85 

Dermatobia 115,  298 

Dermatobia  cyaniventris 163 

Dermatophilus 317 

Dermatophilus  penetrans 60,  126 


Index 


343 


Diamphidia  simplex 55 

Dimoqihism    65 

Direct  inoculators 4 

Diplopoda 25,   257 

Diptera 33,  94,  274 

Dipterous  Larvae 135 

Dipylidium 175,  221 

Dipylidium  canium 4,  175-176 

Dog   flea 172 

Dracunculus 257 

Dracunculus  medinensis 182 

Drosophila 296 

Dum-dum  fever 220 

Dysentery 154 

Ear-flies no 

Earwig 177 

Echidnophaga 317 

Echinorynchus 185 

Elephantiasis    178-179 

Empoasca   mali 33 

Empretia 46 

English  Plague  Commission 171 

Epeira  diadema 18 

Epizootic 170 

Eristalis  137,  295 

Essential  hosts 4,  165 

Eumusca 307 

European  Relapsing  Fever 233 

Euproctis  chrysorrhoea 48 

Eusimulium 286 

Facultative  parasites 131 

Fannia 136,  138,  145,  300 

Federal  Health  Service 169 

Fever,  lenticular 237 

African  Relapsing 230,  234 

Carrion's 253 

dum-dum 154 

European  Relapsing 233 

pappatici 96 

red   water 220 

Rocky  Mt.  Spotted 226 

three  day 96 

Typhus    237 

Filaria 178,221 

immitis 182 

Filariasis   178 


Flannel-moth  larvae 44 

Fleas 119,  166,  213 

cat    1 72 

dog  1 72 

human 172,  176 

rodent 123,  172 

rat 171 

Flesope 125 

Formaldehyde 91 

Fomites 199,  204 

Fulgoridae    28 

Fumigation 320 

Gamasid    68 

Gangrene 129 

Gastrophilus 113,  297 

Giant  crab  spiders 13 

Giant  water  bugs 30 

Gigantorhynchus 185 

Glossina 117,  297,  303 

Glossina  morsitans 214,  217 

palpalis 215,  217,  218 

Glyciphagus    267 

Grain  moth 69 

Grocer's  itch 72 

Guinea- worm    182 

Habronema  muscas 156,  183 

Haematobia 166,  304 

irritans 146 

Haematobosca 304 

Haematomyidium 288 

Hasmatopinus  spinulosus 213 

Haematopota 294 

Haematosiphon  279 

Haemoglobinuria 220 

Hasmozoin 189 

Harpactor 284 

Harvest  mites 60 

effect  of 59 

Head-louse    173 

Helminthiasis 138 

Helophilus 295 

Hemiptera 27,  86,  273-275 

Heteropodidae 13 

Heuchis  sanguinea 55 

Hexapod  larvae 58 

Hexapoda 27,  80,  258 


344 


Index 


Hippelates 297 

Hippobosca 285 

Histiogaster 269 

spermaticus 132 

Homalomyia 136,   138,  300 

Honey   bee 36 

poison  of 37 

Hornets 43 

Horn-fly 137,  304,  308 

Horse-fly no,  165 

House-fly I37-I39,  I44.  183 

control  of 156,  160 

Human  flea 124 

Host,   definitive 175 

intermediate 175 

primary 175 

Hyalomma    264 

aegypticum   224-225 

Hydrocj'anic  Acid  Gas 318 

Hydrotaea    300 

Hymenolepis  diminuta 176 

Hymenoptera 36,  275 

Hypoderma 113,  298 

diana    113 

lineata    113 

lI}^pophar\'nx   80 

Immunity  from  stings 39 

Incomplete  metamorphosis 80 

Infantile  paralysis 162,241 

splenic    220 

Direct  inoculation 164 

Insects  258 

blood-sucking 170 

Intermediate  host 192,  203 

Intestinal  infestation 112,  133 

myasis    137 

Isosoma  69 

Itch    73-74 

mite    73 

Norwegian 77 

Ixodes    260 

ricinus 66,  225 

scapularis 66 

Ixodidae 64-65 

Ixodoidea 62 

Janthinosoma  lutzi 116 


Jigger 60 

Johannseniella    no,  288 

Journal  of  Tropical  Medicine  and 

Hygiene 36 

Julus  terrestris    25 

June  bug 185 

Kala-azar 220 

Kara,    kurte 14 

Katipo  14 

King,  A.  F.  A 3 

Kircher,  Athanasius 1,8 

Kissing-bug 31 

Labium    29,  80 

Labrum 28,  80 

Lachnosterna    185 

Laelaps   266 

Loemopsylla    172 

Lagoa  crispata 45 

Lamblia   intestinalis 154 

Langer,  Josef 37 

Larder  beetles 135 

Latrodectus 12,  14,  17 

mactans 15 

Leishmanioses 220 

Lenticular  fever 237 

Lepidoptera 274 

Lepidopterous  larvae 134 

Leprosy 252 

Leptidae  112 

Leptis 295 

Leptus 60,  273 

Lice    80 

Linguatulina 258 

Liponyssus    265 

Lone  star  tick 228 

Louse,  body 84 

crab    85 

dog  1 76 

head  82 

pubic    85 

Loemopsylla 172,  317 

Lucilia 136,  312 

Lycosa  tarantula 10 

Lycosidae   10 

Lyctocoris 279 

Lygus  pratensis 33 


Index 


345 


Lymphangitis 67 

Lymph  scrotum 178 

Lyperosia 304 

Lyperosiops 305 

Macloskie    34 

Maggots,  rat-tail 137 

Alagnes  sive  de  Arte  Magnetica.  .       8 

Malaria    186 

Malmigniatte    14 

Mandibles  28,  80 

Mange 73-75 

Margaropus 237,  264 

annulatus 223 

Masked  bed-bug  hunter 32 

Mastigoproctus  giganteus 19,  80 

Maxillae 28 

Meal  infesting  species 135 

Melanin  granules 189 

Melanolestes 280 

picipes    32 

Mena-vodi 14 

Mercurialis    i 

Merozoites 190 

Metamorphosis 80 

Miana  bug 63 

Microgametoblast    192 

Midges 107 

Migratorv-  ookinete 192 

Millipedes 25,  257 

Mites 23,  58 

Monieziella 269 

Mosquitoes 33.97.  178,  196,  250 

treatment  for  bites  of .  .  .  .34,  36,  102 
Musca    137,  307 

domestica.  .  .  .  139,  145,  146,  157,  162 

Muscidae    117 

Muscina 137,  146,  307 

stabulans 140 

Mutualism 57 

Myasis 112,  135 

intestinal   135-140 

nasal 141 

Mycterotypus 287 

Myiospila    146,  307 

Myriapoda    25,  132,  257 

Nagana    165,  214 


Nasal  infestation 114,  133 

Necrobia    135 

Nematode  parasite 182 

Nepa    28 

Nephrophages  sanguinarius 132 

Nettling  insects 43 

larva?,  poison  of 53 

Neurasthenia 89 

Nits    86 

North  African  Relapsing  Fever.  .  234 

Norwegian  itch 77 

No-see-ums  109 

Notoedres 269 

cati 78 

Notonecta 28,  277 

Notonectidas 30 

Nott,  Dr.  Josiah 2 

Nuttall 34 

Occipital  headaches 138 

Oecacta    288 

Oeciacus 279 

CEsophageal   diverticula 35 

Oestridae    112,  136 

Oestris  ovis 113 

Oestrus 298 

oocyst 192 

ookinete 192 

Opsicoetes  personatus 32 

Opthalmia 1 55 

nodosa 52 

Oriental  sore 221 

Ornithodoros 65,  260 

moubata    220,  230 

Orthotylus  flavosparsus 33 

Ornithomyia   286 

Oroya 253 

Oscinus    297 

Otiobius 259 

megnini 65 

Otodectes 271 

Pangonia   294 

Pappatici   fever 96 

Parasimulium   286 

Parasite 3,  57.  131.  134.  182 

accidental 3,  131,  134 

facultative 3,  57,  131 


346 


Index 


Parasite,  nematode 182 

stationary   57 

temporary 57 

true 3 

Parasitism,  accidental 134 

Pathogenic  bacteria 152 

organisms   144,  164 

Pawlowsky    81 

Pediculoides    267 

ventricosus 69,  72 

Pediculosis 81 

Pediculus 275 

corporis 84,  233,  238 

humanus    82,  173 

Pellagra 162,  246 

Pernicious  fever 186 

Pest    166 

Phidippus  audax 19 

Philaematomyia    306 

Phisalix    13,  43 

Phlebotomus 289 

papatasii   94 

verrucarum 254 

vexator 95 

Phora 295 

Phormia 136 

Phormictopus   carcerides 13 

Phthirus  pubis 85,  275 

Phortica 296 

Pieris  brassicag 56 

Piophila 297 

Piophila  casei 136,  137 

Piroplasmosis    222 

Plague   166 

bubonic 166,  169,  170 

pneumonic 167 

Plasmodium    186 

Platymetopius  acutus 33 

Plica  palonica 83 

Pneumonic    166 

plague  167,  173 

Poisoning  by  nettling  larvae 53 

Poison  of  spiders 7 

Pollenia 308 

rudis 146,  147 

primary  gland 28 

Prionurus  citrinus 20 

Prosimulium  286 


Protocalliphora 136,  312 

Protozoan  blood  parasite 165 

Pseudo-tubercular   52 

Psorophora   293 

Psoroptes 270 

Psychodidae 94 

Pulex 120,  124,  126,  172,  317 

cheopis 172 

irritans 124 

penetrans 126 

serraticeps 120 

Pulvillus 150 

Punkies   109 

Pycnosoma    308 

Rasahus 280 

thoracicus   32 

Rat  fleas 120,  124,  171 

Rat  louse 213 

Red  bugs 70-72 

Reduviidae 31 

Reduviolus    28a 

Reduvius 282 

personatus 32 

Red  water  fever 220 

Relapsing  fever 230,  233 

Rhinoestrus  nasalis 115 

Rhipicentor 264 

Rhipicephalus 264 

Rhizoglyphus 269 

Rhodnius 280- 

Rocky  Mountain  Spotted  Fever.  .  226 

spotted  fever  tick 67 

Russian  gad-fly 115 

St.  Vitus's  or  St.  John's  dance ....  8 

Salivary  syringe 28 

Sand-flies 109,  25a 

Sanguinetti 11 

Sarcophaga 136,  142,  143 

Sarcophila  302 

Sarcopsylla   317 

penetrans 126 

Sarcoptes 270 

minor  78 

scabiei    73 

Sarcoptidae    72 

Scabies 72,  73,  74,  75 


Iridex 


347 


Scaunis  striatus 177 

Schaudinn 34 

Schizont 189,  190 

Scholeciasis 134 

Scolopendra  morsitans 26 

Scorpions 20 

poison  of 21 

Screw  womi  fly 140 

Sepsidae    296 

Sepsis 136,  297 

Shipley 34 

Sibine 46 

Silvius    294 

Simple  carriers 4,  144 

Simuliidae 33,  104 

Simulium 247,  249,  286,  321 

pictipes    104 

Siphonaptera 119,  274,  316 

Siphunculata 80,  275 

Sitotroga  cerealella 69 

Skippers 137 

Sleeping  sickness 166,  215 

Snipe-flies    112 

Solpugida 22 

Spanish  fly 54 

Spermatozoa 192 

Spinose  ear- tick 65 

Spirochoeta   35 

berberi  234 

duttoni 234 

Spirochaetosis    235 

Sporozoite 189 

Spotted  fever 67,  226 

Squirrel  flea 123 

Stable-fly 137,  160,  163,  165 

Stegomyia 182,  293 

calopus 206 

fasciata    206 

Stomoxys 137,  305 

calcitrans  117, 146,  160,  161,  165,242 

Straw-worm    69 

Stygeromyia 305 

Sucking  stomach 35 

Sulphur  ointment 77 

Surra    165 

Symbiosis    57 

Symphoromyia 112,  295 


Tabanidae    no 

Tabanus 1 10,  166,  294 

striatus 165 

Taenia 175 

Tapeworm 4,  176 

Tarantella  8 

Tarantism 8 

Tarantula    10 

Tarsonemidae    69 

Tarsonemus 267 

Tenebrionid  beetles 127 

Tersesthes no,  288 

Tetanus  129 

Tetranychus 273 

Texas  fever 220-223 

Three-day  fever 96 

Tick 23,  226 

bites,  Treatment  of 68 

fever 230 

paralysis    67 

Treatment, 

Bee  stings 36,  41 

Bites  of. 

Bed-bugs 90,  93 

Blackflies 107 

Bufi'alo  flies 107 

Bugs 31,33 

Centipedes 26,  27 

Chiggers 127 

Chigoes    127 

Fleas 127 

Harvest  mites 61 

Jiggers 129 

Lice    83,  85 

Mosquitoes 34,  36,  102 

Phlebotomus  flies 97 

Sand  flies 96,  107,  109 

Scorpions 22,  23 

Spiders 19 

Ticks    61,68,72 

Ticks,  ear 65 

Blister  beetle  poison 55 

Brown-tail  moth  rash 45 

Cantharidin  poison 55 

Caterpillar  rash 45 

Ear  ticks 65 

House  fly  control 156,  160 

Itch    yy 


Index 


Itch,  grocer's 72 

Lice    85 

Nasal  myasis 143 

Rocky  Mt.  spotted  fever.  .  .228,  229 

Rash,  caterpillar 45 

Scabies 77 

Sleeping  sickness  control 218 

Spotted  fever 228,  229 

Stings,  bee 36,  41 

Typhus  fever,  prophylaxis 239 

Trichodectes  canis 176 

Trichoma 82 

Trineura    295 

Trochosa  singoriensis 11 

Trombidium 60,  273 

True  insects 80 

Trypanosoma 35 

Trypanosoma,  brucei 165 

Trypanosoma  cruzi 219 

Trypanosoma  lewisi 213 

Trypanosomiases 212 

Trypanosomiasis    165,  219 

Testseflies 117,  166,  214,  219 

Tsetse  flies  disease 1 65 

Tuberculosis 155 

Tumbu-fly 118 

Tydeus 271 

Typhoid 155 


Typhoid  fever 1 54 

Typhus    237 

Typhus  fever 237 

Tyroglyphus 72,  131,  268 

Dr.  Tyzzer 49 

Uranotaenia 292 

Vancoho 14 

Varicose  groin  glands 178 

Verruga  peruviana 253 

Vescicating  insects 54 

Wanzenspritze    29 

Warble-flies 112 

Wasps    43 

Whip-scorpions 19 

Wohlfahrtia 143,  302 

Wolf-spiders    10 

Wyeomyia  smithii loi,  293 

Xenopsylla 172,  317 

Xenopsylla  cheopis 171,  124 

Xestopsylla 317 

Yaws    2 

Yellow  fever 196,  203,  205 


^-  f^-  METCALf* 


